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ART. VII.-- On Lazulite, Pyrophyllite and Tetradymite in Georgia;
by CHARLES UPHAM SHEPARD.
difference. The form of me for determinator wished to me af Lin.
WHILE at Allatoona, Ga., in April last, Mr. S. Harris of that place received a small blue crystal from Dr. Stephenson of Lincoln county, the name of which the Doctor wished to learn. It being handed over to me for determination, I found it to be Lazulite. The form of the crystal was well defined, and wholly different from any specimens I had ever seen from Lincoln county, or from elsewhere. This decided me to visit the locality if possible, on my way back to Charleston. On making the necessary inquiries for my route, I learned with surprise, that instead of coming from Lincoln county, N. C., it was from a county of the same name in Georgia, the two being several hundred miles apart.
Want of time however, prevented my reaching nearer than within twelve miles of the spot; but I was fortunate to obtain the assistance of Dr. Stephenson in procuring a supply of the mineral. He was good enough to visit the locality twice, attended by two miners; and has favored me with a description of the circumstances under which lazulite occurs.
The locality is upon Graves' mountain, a ridge three hundred feet high and two miles in length. This elevation is situated about twelve miles northwest of the short auriferous belt, known as the Columbia gold mines in a county of the same name, lying fifty miles above Augusta. Graves' mountain is supposed to be the southwestern terminus of a second parallel gold belt, which extending across South Carolina, includes the famous Dorr mine, and afterwards runs away into North Carolina. The central part of the mountain, to the thickness of fifty feet, is composed of a hematitic rock, which includes in some places an abundance of a ferruginous kyanite, much resembling in appearance the diaspore from the Urals. With the kyanite is found rutile, often in gigantic crystals (weighing upwards of a pound), and possessed of much regularity of crystalline form. The prevailing figure is a square prism with truncated lateral edges, and surmounted at both extremities by an eight-sided pyramid. There is also found a most remarkably perfect twin crystal, in which the geniculation is six times repeated, -producing an hexagonal prism, surmounted at each end by a six-sided pyramid, with a reëntering, six-sided, hopper-shaped cavity, at the tips. These crystals are all more remarkable for their symmetry and polish, than any I have ever seen. Some are fully equal in lustre to the brilliant crystals of cassiterite from Cornwall or Bohemia. The most perfect rutiles are generally imbedded in the massive kyanite, and when detached leave behind impressions having a
polish and lustre equal to that of their own planes. A little common quartz is also mingled with the kyanite and rutile. Occasionally small imbedded crystals of quartz, of the form of those found in the Trenton limestone of New York, are seen in the kyanite.
Closely associated with kyanite, rutile and quartz, are considerable masses (eight or ten inches thick) of a mineral known among the miners of Georgia as steatite, but which is true pyrophyllite, differing in no respect from that of the Urals, except in the finer stellulations it presents, and in the slight ferruginous stain it exhibits near their centres.
The hematite is massive, granular (approaching compact); but the masses are somewhat open, from including the decomposing ferruginous kyanite, particles of pyrophyllite and even portions of compact rutile. The large masses consequently possess a somewhat slag-like and roughened aspect; and suggest, on being handled, the presence of some native metal. It is possible that this hematite may contain titanium as a constant ingredient; in which case it may prove a new mineral.
To the southeast of this fifty feet band, appears the itacolumite, with a thickness of more than three hundred feet, which presents numerous included zones or layers, varying from one to three feet in thickness, in which is found imbedded, masses and crystals of lazulite. The continuity of the lazulite is by no means perfect,—the mineral rather exhibiting a tendency to form nests and bunches. Within a few feet of the surface, the rock is loose and sandy, and presents a pale buff color; but at a depth of three feet, it approaches compactness, with a greyish white color. It is obscurely schistose, with a tendency only to cleavage, and at intervals not nearer than two or three inches. The lazulite is almost wholly in crystals, varying from a quarter to one inch in length ; and are scattered like garnets through granite or mica slate, presenting a very pleasing appearance from the contrast between the ultramarine blue of the mineral, and the clear, pale buff of the rock.
The itacolumite contains traces of gold, especially near the southern extremity of the formation, where it becomes more schistose and embraces minute crystals of pyrites. It has here been worked to some extent for the precious metal.*
* The aspect of many specimens of the hematitic mixture of kyanite and quartz suggests a resemblance to the diamond gangue of Brazil; and I can but regard this spot as well worthy of being examined for the diamond. Dr. Stephenson informs me that at least ten crystals of this gem have been found in Burke county, two in Habersham, two in Hall and one in Union county. The largest of these is said to bave sold for $150 in Philadelphia. The whole number of diamonds thus far found in the United States cannot therefore be less than thirty, nearly all of which occurred in itacolumite.
A greenish, massive kyanite, with scales of white mica (often partially decomposed so as to resemble talc), occurs very rarely in little bunches, in the vicinity of the lazulite crystals. Among these, the naked eye often detects minute and nearly transparent red crystals of rutile. Those of a still smaller size, and visible only with the aid of a lens, are pretty widely diffused through the rock, and often coat the rough surfaces and joints of the lazu. lite crystals themselves.
Small drusy cavities very rarely occur in the itacolumite, pretty nearly filled with barytes, massive and crystalline. Very minute and perfectly formed transparent crystals of quartz are discernible in the barytes, likewise microscopic crystals of sul. phur. The form of the barytes is that represented in fig. 513 of Dana, coming from the gold formation (itacolumite ?) of Fauquier county, Va.
The crystals are represented by the following figures, obligingly furnished by Prof. Dana; and are lettered in accordance with the figure of a lazulite crystal on p. 404 of his Min. eralogy. The rarest of these forms is figure 1, of which I have
detected only three crystals. Fig. 2 is very common, and is the result of a vertical elongation of the crystal, producing a slightly rhombic prism with very oblique dihedral summits, having slightly truncated edges. The planes 2i are always much narrower than in the figures. The crys. 69 tals of the form of fig. 2 are always small, rarely above one-third of an inch in length. Figs. 3 and 4 are unsymmetrical modifications of fig. 1, in which the right hand planes 2 and 2 are horizontally prolonged, and in fig. 4 are possessed of very unequal dimensions, thus giving rise to a very flattened crystal. The crystals of fig. 3 are the largest found, sometimes measuring above one inch in length.
Figure 5, a twin, is by far the most abundant form, equal. ling in frequency all the others combined. It results from the composition of two such forms as figure 1. The plane of composition is coincident with the rhombic base of the figure; and the angle of revolution =180°.
The faces of none of these crystals are suffi. ciently polished to allow of the use of the reflecting gonimeter.
The color of the lazulite is various shades of berlin and indigo blue. The effect of weathering is, to lower the intensity of the blue, and rarely to give rise to a shade of green.
Tetradymite in Lumpkin county. An important discovery of gold has been made during the last summer in the middle of the Chestatee river, four miles east of Dahlonega. It occurs in seams in hornblendic gneiss. Accompanying the gold were found considerable quantities of a white foliated massive mineral, having nearly the color and lustre of tin, which was taken for silver by the miners, though to others it suggested the idea of platinum and even of molybdenite. Several specimens were forwarded to me for examination by Dr. M. F. Stephenson and by W. F. Harris, Esq. I find it to be tetradymite, a species I had before observed in small quantities along with gold, at the Pascoe mine in Cherokee county, and at a place near Van Wort in Polk county.
From the specimens sent, it appears that the gangue of the mineral is gneiss; though in a specimen from Mr. Harris it is diffused in seams through granular white calcite, rendering the mass as heavy as barytes, for which substance it appears, on this account, to have been mistaken.
In both gangues, it is attended by gold. * A number of speci. cimens of the gneiss included with quartz veins, were sent to me for inspection. The quartz veins are transverse to the stratification of the gneiss, and vary in thickness from one to two inches. They contain irregularly shaped masses of pyr. rhotine (intermingled with traces of chalcopyrite), chlorite, angular fragments of green hornblendic gneiss, cleavable calcite, ilmenite in broad highly curved crystals, to which may be added a few crystals of allanite and grains of yellow apatite.t A few
# As it has a very pale brass-yellow color and assays at the mint only from 717 to 800, while the deposit gold in the vicinity varies from 910 to 920, it is possible it may be an alloy of gold and bismuth, analogous to the sample I examined several years ago from the Charlotte, N. C., mint, and for which, in the event of its occuring in nature, I have suggested the name of Bismuthaurite.
+ This is the only instance in which I have detected apatite in the Southern states ; where beryl, also, appears to be equally rare.
grains of reddish garnet are also visible in the gneiss, near its junction with the quartz veins.
The tetradymite is a very handsome metallic mineral. It is broadly laminated for the most part, though sometimes approach ing granular in structure. In one instance it is reported to have occurred in foliæ three or four inches across. I have not seen it in perfect crystals. It contains very rarely, minute forms of a silver-white pyrites not yet determined. The tetradymite when first heated before the blowpipe, evolves a distinct odor of selenium.
When in granular calcite, it is accompanied by small crystals of a brownish, semi-transparent mineral, in prisms resembling tourmaline, but whether they belong to this species I have been unable to determine.
Leadhillite occurs in small quantity at the Morgan silver lead mine, in Spartanburg district, South Carolina. It is associated with pyromorphite and cerusite.
ART. VIII.-Address by Lord Brougham on the Inauguration of
a Statue to Sir Isaac Newton.*
To record the names and preserve the memory of those whose great achievements in science, in arts, or in arms have conferred benefits and lustre upon our kind, has in all ages been regarded as a duty and felt as a gratification by wise and reflecting men. The desire of inspiring an ambition to emulate such examples generally mingles itself with these sentiments; but they cease
* From the London Times, September 23. GRANTHAM, Tuesday, September 21, 1858.-Lincolnshire enjoys the proud distinction of having given to the world the illustrious mathematician and philosopher, Sir Isaac Newton-justly described as “ the greatest genius of the human race"who was born at the manor house of Woolsthorpe, a hamlet eight miles from this town, on Christmas Day, 1642. Sir Isaac was a posthumous child, his father having died, at a comparatively early age, some three months before the birth of a son whose reputation will endure “ to the last syllable of recorded time,” Mrs. Newton re-married, and the embryo philosopher seems to have remained under the care of his maternal grandmother and uncle until he attained the age of twelve, when he was sent to the grammar-school at Grantham. While at school he displayed an extraordinary inclination for mechanics, and busied himself, during the time devoted by his schoolmates to play, in making models of various kinds, chiefly clocks and sun dials, one of the latter of which is still to be seen carved upon the walls of the old manor-house at Woolsthorpe. He was entered, in 1661, at Trinity College, Cambridge, where he was fortunate enough to secure the friendship of the learned Dr. Isaac Barrow, who had been elected Greek Professor in 1660, and who became Lucasian Professor in 1663. In the autumn of 1667, Newton was elected a minor fellow; on the 16th of March, 1668, he was elected a major fellow; and on the 29th of October, 1669, he was appointed Lucasian Professor, in the room of Dr. Barrow, who is said to have resigned with a view to his appointment, and from this period may be dated the development of those wonderful scientific discoveries which have given him a world-wide and time-enduring reputation. It is unnecessary to trace further the career of this great philosopher, orer whose giant intellect a sad