s COMPLIMENTS OF COLUMBIA GRANITE COMP ¥; AN MIDDLETOWN, CONN. ? . an) =. re ee Se ee So ae Scant alte eee hein ees . A DISCUSSION OF GRANITE: Its Essential Properties, Natural Classification, Uses, &c,, together with a Brief Discussion of the Distinctive Characteristics of some of the Leading Granites of the day. JOHN GLENVILLE MURPHY, E.M. (FORMERLY TERRITORIAL GEOLOGIST OF WYOMING). ALSO A REPORT ON THE GRANITE PROPERTY COLUMBIA GRANITE COMPANY. — BY — tRA HoH, WOOLSON, E.M. (OF THE ENGINEERING DEPARTMENT OF COLUMBIA COLLEGE, N.Y.) 4 wr'tS Zot Py M2 rH ( \) GRANITE As a Stone in Building and Construction. Building-stone requires accurate obser- vation combined with practical experience in the field. A knowledge of the mineral con- stituents may be obtained from standard text- books, but nothing more. This will be clearly seen as we proceed with our subject. Building-stone must be studiedwith reference to its hardness, durability, beauty, chemical com- position, resistance to crushing force and struct- ure. It is evident that the durability of a stone does not depend on its hardness or the strength of a sample alone. Equally, if not more impor- tant in this respect, is the chemical composition. Each must be studied in its order, and we will confine ourselves to the granitic rocks. as their superiority over all other stone used in construc- tion is now recognized by architects, builders and engineers. In giving the strength of granite produced in the -principal quarries we shall quote from the elke ACQUIRE a thorough knowledge of 3 most reliable authorities. The durability and capability of resisting climatic influences depends primarily upon the chemical composition; but, as the granite from the principal quarries has not been studied with reference to this important factor, we can make no comparisons in this respect, GRANITE. Very few people can be found who are willing to confess ignorance with regard to what they deem so simple a rock as granite. The book student will say that it is a rock made up of the minerals quartz, feldspar and mica, and thinks he has exhausted the subject. The layman will say, ‘‘Why, it is the stone in such and such buildings, and in this and that wall,” and express surprise that so simple a question should be asked. As a matter of fact, the subject is ex- tremely difficult, and in the following discussion we will ask — first, the indulgence of the student, and second, his careful consideration of the facts herein presented. We have studied all the stand- ard works on the subject and find much con- fusion. CRYSTALLINE SILICIOUS ROCKS. Of this group we shall only consider granite, syenite and gneiss. In commonor quarry nomen- clature these rocks are termed granites, and in- deed it is often difficult to determine to which 4 class a particular rock belongs; and we may safely say that it is impossible to separate them in field practice if the definitions of the authorities are followed. ‘Granite consists of quartz, feldspar and mica.” —DANA’sS MINERALOGY. ‘*Syenite consists of quartz, feldspar and hornblende.” —DAna’s MINERALOGY. **Gneiss consists of quartz, feldspar and mica, possessing cleavage planes.” —DANA’s MINERALOGY. ‘* Gneiss is a Stratified granite.” —Dr. HAwes, Report, Vol. 10, Tenth U.S. Census. He says: ‘‘ The gneisses or stratified granites are extensively quarried, and stratification is a circumstance very favorable to the extraction of the stone for some purposes. For example, the perfection of cleavage incertain directions makes it easy to split large slabs from the mass, to be used for curbing, paving, steps, etc. The stones can be split in such a way as always to possess two parallel flat surfaces—a circumstance which _ Simplifies the construction of walls from them. There are no uses to which granite can be ap- plied to which the gneis$oid rocks cannot also be applied, and some of the largest quarries in the United States, which are designated granite quarries, really produce gneiss.” —Vol. 10, Tenth U. S. Census. 5 We cannot say that the definitions of Dana are incorrect, inasmuch as these rocks contain all the minerals mentioned. It will be seen, however, that most granites contain other min- erals. The definition of gneiss can be called faulty, inasmuch as the physical difference be- tween gneiss and granite is not noted, and which is in reality the only difference between the two stones. The article of Dr. Hawes written for the tenth census is not merely faulty, but mislead- ing, and much mischief may result from it. The term ‘‘ stratification” is used for ‘‘ cleavage.” A moment’s thought will show this to be incorrect. Cleavage comprehends stratification, and much more; for example, crystals possess parallel cleavage on the crystalline planes, which cannot correctly be called stratification. Again, it seems to be implied that all granite which ex- hibits parallel cleavage is gneiss—we use the term ‘‘exhibits” in the sense that is evident on mere inspection, for all granite will be shown to possess parallel cleavage. This is a serious error; for all fine-grained granite has distinct cleavage planes, and the stone produced in some of our most famous granite quarries would be called gneiss. So important a matter as this requires careful consideration. To express the property which some rocks have of more readily splitting on one plane than on the other, four words are com- monly used as synonyms—viz., cleavage, stratifi- cation, rift and lamination. As applied to gran- ite, a moment’s thought will show any one that 6 the terms lamination and stratification are not at all applicable. The term rift, used by all quarry- men, is applicable to massive granular rocks, and signifies the plane of easiest cleavage—that is, facility to split in a particular direction. The term cleavage is equally proper, but more gen- eral in its application; so that the term rift, being specific for its particular purpose, will be adhered to. That all granites possess more or less rift is a well-known fact, and we hear the quarrymen speak of the stone from a particular quarry as having a good or bad rift. We never hear them speak of a granite in which the rift is entirely absent. The rift is a very important considera- tion to quarrymen, since to its greater or less perfection is due the ease with which a stone can be quarried or worked into forms. That all granites possess a rift is also well known to engi- neers and experimenters who test the stone for the purpose of determining its resistance to crushing force. They speak of the samples as being tested on bed or onedge. The so-called bedding in this case is coincident with the rift. Cleavage planes, or the rift in granite rock, results from two causes, viz.: Pressure, or the aggregation of a portion of the mica into parallel layers. ‘A moment’s reflection will show that the first cause must be general, from which, as well as the experience of quarrymen, it results that all granites havea rift. The second cause is not general, from which it also results that there is a distinct physical 7 difference in granitic rocks. (We will return to this under the head of Gneiss.) The rift in true granite is caused solely by pressure, and its greater or less*perfection is governed by two causes, viz.: first, the amount of pressure to which it has been subjected during solidification ; and second, the size of the crystal- line particles of which the rock is composed. We may assume that the pressure sustained by granite forming the outer crust of the earth is practically the same for all sections, no matter how distant (since the pressure was that due to the superincumbent mass during solidification and the amount of erosion since that time necessarily very great), so that we need consider the size of the crystalline particles alone as affecting the rift. From this it results that the finer the crystalline particles the more perfect it is; and as the crys- talline particles increase in size, the more faintly evident it becomes, and finally, when the crystals become very large and the granite necessarily coarse, no rift is evident by mere inspection, though its existence and direction is well known to the quarrymen who work it. GNEISS.. Totally different from the foregoing are the cleavage planes or rift caused by the aggrega- tion of a part of the mica into parallel layers or | planes, which, in additien to causing the stone to split readily into slabs having flat parallel surfaces, also weakens it along the line of these planes, which is not the case with the cleavage 8 planes resulting from pressure. (See result of tests made by Mr. I. H. Woolson, of the En- gineering Department of Columbia College, New York, annexed to this report.) We may say, then, that gneiss consists of quartz, feldspar and mica, possessing parallel cleavage planes due to the aggregation of a portion of the mica into parallel layers. The physical difference just noted is alone what separates gneiss from granite. In distinct- ive types of each stone the difference is quite striking. We have found that there is merely a physical difference between granite and gneiss; from a mineralogical or chemical standpoint, they are the same. Granite and syenite are physically the same, while they differ simply in the fact that in syenite the mica is replaced by hornblende. As these two varieties of stone are the most im- portant rocks used in building and construction, we will consider them with care. Granite is defined as a rock consisting of quartz, feldspar and mica; syenite is a rock con- sisting of quartz, feldspar and hornblende. Be- tween these distinctive types we find nine-tenths of the commercial granites, and we hear such terms as hornblende granite, hornblende-mica granite, epidote granite, syenitic granite, gran- itie syenite, etc., etc. Commercially these rocks are the same, no matter whether they consist of quartz, feldspar and mica, quartz, feldspar and hornblende, quartz, feldspar and pyroxene, or a mixture of all these as well as other minerals. 9 Structurally the stones are the same, which perhaps accounts in a measure for the commercial acceptation. Naturally, where the eye alone is used for inspection, structure alone is regarded ; and we would ask if this is not the safest as well as the less embarrassing plan? If a chemical classification is attempted it results in confusion to the ordinary business man, who simply wishes to know that a good, durable stone is to be em- ployed. Tell him that he is to have a harnblende- biotite granite, which contains no pyroxene and but little pyrites, and in nine*cases out of ten we would be met with a look of amazement, and the answer that it was his business to pay for his structure when it was completed in accordance with the specifications, and our business to fur- nish acceptable material. What surprises us mostly is that all these so- called varieties are not comprehended under one name—viz., granite or syenite. Let us examine the question critically, and see if it would be war- ranted. A stone which tothe naked eye consists almost exclusively of quartz, feldspar and mica is called by the best writers typical granite ; but other writers introduce confusion even here by subdividing this, the simplest form, into several classes, according to the kind of mica. Thus, when the mica is a white muscovite, they give us a muscovite granite. When a dark biotite mica, a biotite granite, and when the stone contains a fair proportion of each, a muscovite-biotite gran- ite. Here is the first stumbling-block to the honest searcher aftertruth. He has under consid- eration several pieces of granite. One contains - Io quartz and feldspar, with the muscovite and biotite micas about equally distributed. Another contains the-same minerals, but about four times as much muscovite as biotite ; another about four times as much biotite as muscovite; another contains both micas, but a very small proportion of the biotite—yet enough to be distinctly visible, etc., etc. We would now ask the reader to clas- sify these granites if he wishes to do so. If we are asked to doso, we shall be pleased to answer, “This is a typical granite ’””—or, more broadly— ‘This is granite.” ” A stone which consists almost exclusively of quartz, feldspar and hornblende is called in like manner by the best writers a typical syenite. (We will say here that the typical granites and syenites, so-called, are never found extensively in large quarry operations.) We rarely find a stone which contains an appreciable amount of hornblende without pyroxene. See Quincy, North Conway and Cape Ann granites. It is also rare to find extensive bodies—we doubt their existence at all--of granite without mica, so that again voluminous writers confuse us with such terms as syenitic granite, granitic syenite, hornblendic granite, hornblende-pyroxene gran- ite, pyroxenic syenite, micaceous syenite, horn- blende-biotite granite, etc., etc. What will our earnest searcher after truth do here? These minerals occur in granite or syenite, if the latter term is preferred, in very variable pro- portions. When there is visible to the naked eye four, six, eight or fifty times as much horn- blende as mica or pyroxene in the rock, what It shall we call it? We cannot call them impure granites or syenites, as this would imply imper- fection, notwithstanding that a stone which con- tains hornblende and mica may be an excellent granite. We have now reached the point at which we have been aiming—?. e., May not the scientific world with propriety adopt the same term as the commercial world for these different varieties of the same stone, and thus save endless confusion by reducing the subject to the simplicity which really belongs to it? We think so: let us see. Structurally all these varieties’ are undeniably the same—have they the same origin? We believe so, and that they form the great mass of the prim- itive rock. Many writers recognize—in their writings—metamorphic and vein granites. That granitic structure may have been produced on the small scale by metamorphic action and vein deposition may be admitted, but we doubt that any considerable body of granite has been so formed. We will return to this again. Let us pass through geologic time and conceive the con- dition of our globe when it was a liquid mass revolving in space, with our seas, lakes, rivers, etc., existing in the shape of steam and vapor in the outer chromosphere. Let us follow the gradual subtraction of heat and consequent gradual solidification of the earth’s crust, due to radiation. The same laws of force then as now governed the mass. That is to say, our orbit was the trajectory, resulting from an equilibrium between centrifugal and centripetal forces, and the law of gravity also was the same then as now. 12 Hence, we readily see that the heavier metals and compounds would be drawn toward the centre, the lighter materials forming the outer crust. Now, since the same forces were in opera- tion all over the earth’s crust, it results that sim- ilar effects were produced—that is to say, the crust all over the globe must have been similar ; but this crust constitutes the whole of the primi- tive rock, from which it results that the primitive rock must be similar structurally, though abso- lute chemical uniformity cannot. be expected, as will be shown. The slow cooling of the mass accounts for the crystalline structure ; but it may be asked, What evidence have we that the primi- tive rock is granite or syenite? We answer, that the great mass of the earth’s crust at this day is composed of granite and the minerals resulting from its disintegration. The great subdivisions of the rock constituting the earth’s crust are the primitive, sedimentary, volcanic, plutonic and chemical— with the plutonic we include the meta- morphic. After the solidification of the primitive crust and the continuous radiation of internal heat, moisture was deposited which would flow to the greatest depressions, producing disintegration and erosion of the crust already formed, which, being deposited by the waters and reconsolidated by pressure and heat, form the sedimentary rock. Metamorphic rock consists of these deposited sediments re-fused and crystallized, and some writers class as metamorphic such portions of the primitive rock as may also have been re- fused and crystallized, but the sedimentary and us metamorphic rock taken together consists of the elements of granite. Furthermore, the great mass of rock fronting our sea-shores is granite. In great mountain upheavals the peaks are invariably granite, be- cause even if originally sedimentary, the great denudation at the exposed peak in time reaches the granite ; there can be no question, then, that granite is the primitive rock. We have shown that all granites possess cleavage planes, or rift. That this must.be the fact seems evident ; for, since the formation of the crust great erosion has taken place, and is measured by the total sedi- mentary rock, part of the metamorphic plus the greater part of the gravels and sands; conse- quently, the granite exposed on the surface to- day existed at great depth at the time of its forma- tion, and was therefore exposed to great pressure from the superincumbent mass. This pressure must have interfered with the formation of per- fect crystals, and flattening took place on the points exposed to this pressure, resulting in cleav- age planes or rift, at right angles to the line of pressure, as announced in the first part of this article. It has been shown that, in accordance with the law of gravity, the lighter material of our globe should form the earth’s crust, or the primi- tive rock. That this is what has actually taken place is shown by the fact that, while the specific gravity of the whole earth is 5.5, that of the crust will not average more than 2.6; hence we should expect the primitive rock to be formed chiefly of silica and the silicates, quartz, feldspar, mica, 14 hornblende, pyroxene, epidote, garnet, tourma- line, chlorite, etc. By microscopic examination, no less than thirty different minerals have been found in granite—(see Vol. 10, Tenth U. S. Census)— which should teach us to avoid chemical classifi- cation. Now, while the magma composing the earth’s crust contained so many different minerals, is there anything which would lead us to believe that their distribution was uniform? It is even absurd to suppose that such would be the case. Even in blast-furnace practice, where the ore and flux are mixed with ail possible care, we never- theless find some slags acid and some basic. The idea that nature would produce an exact division and arrangement of the elements forming its magma over so enormous a space is not to be entertained. Hence we find similar structure but variable composition. The quantity of quartz and feldspar even is variable —(see analysis of granites in any of the standard authorities)—but this is not only true of granite from different quarries, but also of the stone in the same quarry. If we have shown that all granites and syenites are the same, not only structurally, but that they have the same origin, why not adopt a single name for all of them? Call the rock either gran- ité or syenite, and much confusion will be avoided thereby. We have stated that we doubt if any consider- able bodies of granite have been produced by metamorphic action or in vein filling. It is evi- dent at the outset that the erosion of the primitive bs) rock by the action of water must also have produced a sorting and rearrangement of the materials. Thus a stone which originally con- sisted of quartz, feldspar and mica, when disin- tegrated and the materials transported by water to considerable distances, would deposit the heavier and coarser material first, while the thin flakes of mica would be carried to much greater distances ; consequently, any metamorphic gran- ite must be such as has been re-fused and recon- solidated in place. The reader can decide if he thinks much of this has taken place, or whether it should be called metamorphic granite at all. We hardly think it worth while to discuss the possi- bility of the existence of any considerable bodies of vein granite ; a moment’s reflection will show the absurdity of such an idea. We will now proceed to a more particular discussion of granite. ESSENTIAL ELEMENTS OF GRANITE. We can with propriety divide the minerals of a granite into essential and accessory elements, the essential elements being those which are invariably present and form nearly the whole mass of the rock, while the accessory elements are those which exist in small or minute quantity and even in some quarries may be entirely absent. The essential elements are quartz, feldspar, mica and hornblende. (Pyroxene and epidote in some varieties of granite become essential elements by taking the place of the hornblende 16 or mica wholly or in part—see light green variety of North Conway granite and the deep green variety of the Adirondack Granite Company— this, however, is not of frequent occurrence). Among the most frequently occurring accessory elements are pyroxene, epidote, pyrites, chlorite, garnet, tourmaline, magnetite and the oxide of iron (rust), as a decomposition product. Granites are spoken of as being light gray, gray, dark gray, cream-colored, pink, red, green (as seen in some varieties of the Adirondack stone), and purple (Swedish granite). There are also gradations and blending of all the colors above mentioned. Let us consider the essential elements and the modifications of color produced by them, If the minerals were precisely the same in physical appearance, chemical constitution, and the crys- tals were of the same size, then granite would be invariable. Suchis not the case, however; the elements vary in color and in the size of the crystals, so that we find a striking difference in color and texture not only in granites’ quarried in different sections, but also in the same quarry. Pure quartz consists of silica (Si, O;), two chem- ical elements, silicon and oxygen. As it occurs in nature 999 parts in 1000 are not pure. The amount of impurity is variable in character and quantity, thus modifying its color and appear- ance. In color it passes through all gradations from white (milky quartz) to black (flint). Thus we have the quartz crystal, agate, carnelian, amethyst, etc. It is also transparent, translu- cent or opaque. 7 Feldspar is a complex silicate, consisting of the silicates of alumina, potash, soda and lime in varying proportions. (The chemical discussion of the elements would occupy too much space, and will be omitted for that reason). In color it is gray, yellow, pink or red. Mica is also a complex silicate; colors, white (muscovite), black (biotite). Hornblende, pyrox- ene and epidote are also complex silicates ; colors, white, passing to green and black. We see, therefore, that there is a most marked difference in the essential elements of granite, from which it results that it is very variable in color. Another modification results from the difference in the size of the crystalline particles, so that we recognize coarse and fine grained granite. The most important differences, how- ever, result from what are improperly called ac- cidental impurities, and which affect the value of the stone for all construction purposes. ACCESSORY ELEMENTS. The consideration of the accessory elements forms by far the most important factor in the in- vestigation of granite, of which no less than thirty have been found in the various samples submitted to microscopic examination and chem- ical analysis. We will only consider those which occur in appreciable proportions, and play an important part in the modification and value of the stone. Hornblende forms an essential element in many of the granites, but it also 18 occurs in many varieties in small proportion, and is then considered an accessory element. The others are pyroxene, epidote, chlorite, tour- maline, garnet, magnetic and titanic iron, iron pyrites and the oxide of iron, as a decomposition product resulting from the oxidation of the pyrites. Some of these elements, as hornblende, tour- maline and garnet, are not objectionable where strength alone is considered. Pyroxene, epi- dote, chlorite, titanic and magnetic iron are det- rimental to granite as accessory elements, but the pyrites is more detrimental than all the other elements combined, and is of far more frequent occurrence; in fact, a close inspection will show its existence in many of the so-called standard granites, which on exposure to atmospheric action produces an unsightly stain of iron rust (oxide of iron). This element is also damaging to the stone by aiding and, when in any considerable quan- tity, producing disintegration of the whole mass. It will then be seen how important is the chem- ical determination of the constituents of granite, and that hardness or resistance to crushing force alone is not sufficient to determine the relative value of granite; nor is it safe to accept stone from any quarry without an examination, for the quality of the stone varies even in the same quarry, and one contract might be filled with stone that would be entirely satisfactory, while the stone supplied for another would be much inferior. Many people will recommend and use stone from a particular quarry because stone 19 from that quarry has been used for a number of years and has given satisfaction. This they do on the erroneous assumption that the quarry will always produce stone of the same quality. The practice is not only dangerous but expensive, as many new quarries produce a superior stone and sell it cheaper. The only safe plan is to make an examination of the stone which it is proposed to furnish. We have said that stone should be studied with reference to its hardness, durability, beauty, chemical composition, resistance to crushing force and structure. Let us briefly consider these qualities. Hardness is very desirable, because it admits of working the stone, so that sharp, well-defined edges are produced. Itis not so readily scratched and defaced, and is one of the requisites of durability. The durability of a stone depends on its hardness, resistance to crushing force and chemical composition. Ifa stone contains an element which is soluble in atmospheric waters, then it is unfit for building purposes. Also if a stone contains a mineral which is soluble in acid waters, it is unfit for use as a building stone in manufacturing centres. None of the essential elements of granite are soluble in any of these waters; but when it con- tains pyrites as an accessory element, then it contains a material which by change becomes soluble. The first change which it undergoes on exposure to atmospheric action is oxidation, by which the sub-oxide of iron and some sulphate of iron are formed. At this stage both are solu- ble in water and are washed out. The next stage 20 is per-oxidation, by which an insoluble oxide of iron(rust)is formed. The effect of these changes is seen in buildings constructed of stone which contains even a small percentage of the pyrites. The sub-oxide of iron is formed, which being soluble, is washed out of its place by rain-water, and which, spreading over the face of the stone, becomes partly per-oxidized, forming unstghtly stains of iron-rust;.this effect is seen in any building constructed of stone which originally contained this mineral. Its occurrence in build- ing-stone is more frequent than is generally supposed. The beauty of a stone depends upon its purity, freedom from undesirable accessory ele- ments, hardness which gives it form, and struct- ure. The question of color is a matter of taste. The stone should be free from pyrites, pyroxene, epidote, etc. It should be regular in structure, that is, the quartz and feldspar should not occur in bunches or aggregations (termed ‘‘ white horse” by the quarrymen). The mica also when in bunches detracts from the beauty of a granite. For general use a fine grained stone is much hanasomer and stronger than a coarse grained one, except perhaps for use in large columns, where the coarseness of the crystals will not ap- pear to such disadvantage. The importance of the chemical composition, resistance to crushing force and structure have been considered and discussed in the preceding part of this article. The characteristics of the granite from some of the most important quarries in point of public favor might be noted. The Quincy granite contains both hornblende and mica, but the former in much the greater proportion. It isa coarse-grained stone, quite dark when polished, and mottled in appearance, because of the large amount of hornblende, and also that some of the quartz is transparent. It contains some pyroxene, which is brittle and friable, as can be seen in the numerous holes in a hammered face. It also contains iron pyrites in appreciable proportion, as can be seen in old monuments and in buildings where the stone has been exposed to atmospheric action for five or six years. The granite quarried at Cape Ann (at Rock- port and Lanesville) contains both hornblende and pyroxene and but little mica. The chief in- dustry is the manufacture of paving stones and coarse ashlar, because the stone contains more - iron as an accessory element than the Quincy, which, as shown, is detrimental for fine work. It is also a coarse-grained stone. The North Conway, N.H., granite is coarse- grained ; colors, red and green. The red is the principal variety; it contains both hornblende and pyroxene, no mica. The green variety con- tains epidote and chlorite, in addition to the hornblende and pyroxene. This variety is used chiefly for paving. The railroad depot at Port- land, Me., is constructed of the red stone, and notwithstanding its coarseness, looks well, as it is used in large blocks and columns. The Maine granites in general are coarse- grained, the exceptions being the Hallowell and Friendship stones. The latter stone contains 22 enough pyrites in the samples we have seen to be extremely detrimental. (See the arch at the entrance to Prospect Park, Brooklyn, N.Y.) The Hallowell stone deserves particular at- tention, as it has attained a high rank in public favor. It is fine-grained and comparatively pure; color, gray; mineral constituents, quartz, feld- spar and mica, mainly- the white muscovite variety of this mineral. The feldspar is the white albite or soda spar; quartz, opaque. It is a good stone, but by no means what we would consider a high class granite, though it is exten- sively used for statuary. The stone is readily worked and the rift is plainly evident. The granite quarried at Concord, N. H., is . known as silver granite, which name is due to the fact that fhe stone contains an excess of white muscovite mica, which occurs in flakes possess- ing in this form a silver lustre. It is fine- grained; color, gray; rift, evident. This stone has received much favor for some purposes. Constituents, opaque quartz, soda feldspar and white muscovite mica. The granite quarried at Millstone Point, near Niantic, Conn., would be a strictly first-class stone were it not that it contains considerable pyrites. It is fine and close-grained in texture. Constituents: Quartz (opaque to translucent), feld- spar (part sodaand part potash spar), mica (mostly biotite with some hornblende in fine, needle-like crystals). The stone is massive; rift not dis- tinctly visible by inspection. The granite which was formerly quarried at Groton, Conn., was very similar to Millstone rock. 23 The most famous quarry operated up to this date is known as the Smith Quarry, located near Westerly, R. I. Structurally it resembles the stone of Millstone Point and Groton, Conn., but in color it is slightly different, being what quarry- men would call richer. In a rough sample the difference in color is not so evident, but in pol- ished samples it is quite distinct—the Millstone ona polished surface showing dark gray, while the Westerly has a distinct tint of brown. This difference is due to the fact that the Westerly contains more potash feldspar. Minerals same as Millstone. In conclusion we would say that architects, engineers and builders have not always the requisite facilities for determining the value of a material for use in construction, but they can always have it done without much expense. The resistance to crushing strain can be determined at the establishment of the Messrs. Fairbanks & Co., or more accurately, at the School of Mines, Columbia Coliege, and the U. S. Arsenal at Watertown, Mass. The resistance to crushing force which any stone should stand will in most cases be estimated by the use to which it is put. Thus the strongest stone should be selected when it is to be used in a position that will be subjected to great pressure. When it is proposed to use a stone for exterior work, its adaptability to the atmospheric con- ditions should be noted. Thus, any building- stone containing limestone as an ingredient should not be employed when it is to be sub- jected to acid conditions of the atmosphere, as at 24 as Pittsburgh, Penn., Trenton and Newark, N. J. etc., or any large manufacturing centre, as de- facement and disintegration of the stone will be rapid. Any material adapted for exterior construc- tion should be free from pyrites. The existence of this mineral will not weaken the stone in a fresh sample, nor is its existence in small quan- tity readily detected, except by chemical analysis. A very small quantity is exceedingly detrimental to any stone which is destined for building or ornamentation. GRANITE THE STONE OF THE FUTURE. There are no uses for any stone used in con- struction to which granite cannot be applied. When pure and fine-grained it offers great resist- ance to crushing force, and is not disintegrated by any atmospheric conditions. Itiswelladapted “to ornamentation as it takes a high polish, and also finishes under the hammer and chisel to sharp and regular edges. It can be worked into any forms to which even marble is susceptible. The light gray varieties of granite produce by far the most beautiful statuary; though more expensive to produce fine work from it on the start, it more than compensates this drawback by being practically indestructible when produced. JOHN GLENVILLE Murpnuy, E. M. 25 Part I1.-A New Granite. The granite to which we especially wish to call attention was recently discovered near the Narrows of the Connecticut River, four miles southeast of the city of Middletown, Conn. It occurs on a high bluff fronting the river on the west shore, and is described in the accompanying report of I. H. Woolson, E. M., of the Engi- neering Department of the School of Mines of Columbia College. This report speaks for itself. With regard to the tests, we may say that they ase the most thorough and extensive series of tests ever made upon stone from a single quarry, and forcorroborative evidence we sent four cubes to be submitted to a compressive strain at the Government Hydraulic Testing Machine at the U.S. Arsenal, Watertown, Mass. The remark- able resistance is given herewith, and fully con- firms the results obtained by Mr. Woolson. The owners of the property, now the Columbia Gran- ite Company, desired to have an exhaustive examination of the stone made for their own knowledge, and also to satisfy the public that the granite was of exceptionally high quality in all respects. Their most sanguine expectations have been more than realized. NEw York City, July rith, 1892. COLUMBIA GRANITE COMPANY, MIDDLETOWN, CONN. GENTLEMEN—I have lately visited your gran- ite property at Middletown, as you requested, 26 x and carefully examined the various ledges ex- posed. I have also made an exhaustive series of tests upon the crushing strength of samples taken from the different out-crops, and respect- fully submit the following report: The property is located on the Connecticut River, four miles below Middletown, and is one of the most delightful spots along the shores of that beautiful river. The property contains fully a thousand acres, and the supply of granite on the same is ‘practically inexhaustible. The ledges are numerous and prominent; they stand out boldly from the surrounding soil, and present the finest opportunities for quarrying purposes. They run continuously across the property, nearly parallel with the river, for a distance of over two miles, and in many places they project forty to fifty feet above the surface, thus exposing hun- dreds of thousands of tons ready for excavation without any ‘‘ stripping” whatever. The ship- ping facilities are of the best. With a railroad directly through the property, and two and one- half miles of river front, it is difficult to see how they could be much improved. There seems to be no doubt that the property is capable of being developed into one of the largest and finest granite quarries in the country. The quality of the stone is excellent, as is con- clusively shown by the accompanying report of tests. It is of two varieties and in amount about equally divided betweenthem. One is a coarse- grained granite of reddish cast, due to the flesh- colored feldspar, and contains a moderate amount of fine black mica. It is susceptible of gocd a7, polish, and will make a beautiful and effective stone for architectural purposes, while its great strength will adapt it for use in piers, founda- tions of large buildings, arches or any place where it will be subjected to heavy crushing strain. The other variety is a very fine-grained, light gray stone of exceeding beauty and strength. Its crystalline structure is particularly compact and uniform. It breaks with a clean, sharp fracture, the surfaces of which are almost glassy in appearance. It possesses a most extraordi- nary toughness and resistance to crushing force, which qualities render it particularly desirable for use in places where it will be subjected to excessive wear and shock, as in paving, curbing and the like. It takes an elegant polish, and this fact, together with its fine grain and uniform structure, admirably adapts it for monumental purposes or ornamental use of any kind where chiseled surfaces are required. Neither of the varieties show any trace of iron, which is decid- edly in its favor, for many otherwise good gran- ites are ruined for building purposes by the presence of this impurity. In the question of strength this stone is quite phenomenal. From the following tabulation of results and the report of tests, it will be seen that a series of nine (9) tests which I made upon 2-inch cubes of the coarse-grained stone from the ‘‘N.W. end of Ledge” gave an average of 23,000 lbs. per sq. inch, and a similar series of seven (7) tests made upon samples taken from the ‘‘ Middle Ledge,” gave an average of 22,000 28 Ibs. per sq. inch, or an average of 22,500 lbs. for the sixteen (16) specimens, thus demonstrating the extreme uniformity in quality, for these samples were taken from places distant from each other fully 4000 feet. Nine (9) SAMPLES FROM SEVEN (7) SAMPLES FROM ‘““N.W. END OF LEDGE.” ‘* MippLE LEDGE.” Lbs. per sq. inch. Lbs. per sq. inch. Pa.00). =. bed. 21,460 - Bed. 21,450 - Edge. BE QOD els eas 2E019 = vy 24,753 - pA 24,278 - 4; 21,921.- = 2 22,525 - Bed. 22,197 - Edge. 22,475 - a 21 831 - fi 23,525 - ee 20,470 - 4 25,450 - Edge. 23,542 - Bed. 207,264 9 —23,029 155, 290-7 =22,184 23,029 22,184 45,213 —2—22,600 This average of 22,600 lbs. per sq. inch for the whole of the red variety is.exceedingly high, but even this is small when compared with the results obtained from the gray granite. On this latter variety I made tests upon twelve (12) cubes cut from samples taken from different parts of the ledge. 29 The average of the whole gave the extraor- dinary result of 31,600 lbs. per sq. inch, while one specimen stood 34,000 lbs. per sq. inch. TWELVE SAMPLES OF FINE-GRAINED GRAY GRANITE, Lbs. per sq. 7n. 8205 4. eds $1,019... >, =a 82.700). 35): ee 30,050... SS eas 32 000) Js eke sue Reels 82,562... - {ines 30:000° 29,4005," <)> >) alee 34,0754. = ee 39 0507, "