MINERALOGY; WITH A CLASSIFICATION OF SILICATES. 69 



but coutaiuing- a large proportion of copper.' Contndophilite follows, with 4:4:4, and the 

 more siliceous roigtite, 4 : 4 : 8. a hydroiTs biotite. From this we pass to jetferisite, 4 : 6 : 10, 

 a highly hydrated species having the same ratio of protoxyds and sesquioxyds as 

 thuringite, and as the more basic and nearly anhydrous seybertite, 4 : G : 3J. Following 

 these, among hydrous species, are willcoxite, chloritoid, oellacherite, margarite, cookeite 

 and damourite. We hare, in f\ict, throughout the whole protoperphylloid tribe, from 

 phlogopite to muscovite, an anhydrous and a hydrous series, and the chloritic group is 

 made up of the more highly protobasic members of the latter. In these comparisons we 

 haA'e generally deduced the atomic ratios from the formulas given in Dana's "System of 

 Mineralogy," which represent approximately the results of chemical analysis. The late 



' Tliis species, wliicli was described liy the writer in 1876, is found in tlie .Tones (or .Toliannes) Mine, in 

 Carnarvon, Bucks County, Pennsylvania, long known as a large deposit of maguetite associated with cbalcopyrite, 

 malacliite, ohrysocolla and a substance wliicb bad bitlierto been called clay-carbonate copper ore, of wbich several 

 tbousand tons, yielding from six to seven per cent, of copper, had up to that time been mined and utilized in smelt- 

 ing. Tliese ores are found in tlie Taconian crystalline scbists of the region, tlie so-called Primal slates of Rogers, 

 and tlie mineral in question is distributed in greater or less abundance, tbrougb several feet of the strata, ahei-nat- 

 ing with layers of a coarse granular material poor in copper, the whole marked witli ferruginous bands which 

 coincide with the bedding, and intersected with veins of quartz : layers of half an inch or more in thickness were 

 found to contain ten or twelve per cent, of copper. 



"These pure portions have a pea-green or apple-green color when moist, becoming greenish-white on drying, 

 when the Jiiass falls into a powder, wdiich is seen under the microscope to consist of minute, transparent, shining 

 scales, mixed however with some grains of quartz and a small portion of magnetite. A qualitative examination of 

 this material .showed that it contains no carbonates, and is not of the nature of a clay, but consists of a hydrous 

 silicate of magnesia, copper-oxyd, alumina, and iron-oxyd, constituting a kind of copper-chlorite. It is but feebly 

 attacked by dilute acids, while strong acids, and notably sulphuric acid diluted with two or three parts of water 

 and aided by a gentle heat, readily and completely decomposes it, with separation of tlocculent silica, which, by 

 solution in dilute soda-lye, is readily separated from accompanying quartz and magnetite. A single somewhat 

 rough analysis made in this way, gave me, for 100 parts, — insoluble sand, 14.10; silica, 24.00; alumina, 13.00; 

 magnesia, 15.1.5; ferric oxyd, 7.11; cupric oxyd, 15.30; water, 11.50= 100.70. The qualitative examination of a 

 considerable portion of another and less pure specimen, gave an apprecialile quantit}' of zinc, and a distinct trace 

 of nickel. A jiortion of the sjiecimen of tliis copper-silicate of which the analysis is given above, was freed by 

 careful washing alike from the coarser grains and from the lighter portion, which remained long suspended in 

 water. The material thus purified was somewhat richer in copper than before, and has been carefully analyzed 

 by my friend, Mr. George W. Hawes, of New Haven, who found insoluble sand, G.22 ; silica, 28.93 ; alumina, 

 13.81; ferric oxyd, 5.04; ferrous oxyd, 027; magnesia, 17.47; cupric oxyd, 1G..55; water, 12.08 = 100.37. This, 

 deducting the insoluble matter, gives for 100 parts : silica, 30.73 ; alumina, 14.G7 ; ferric oxyd, 5.35 ; ferrous oxyd, 

 0.29 ; magnesia, 18.55 ; cupric oxyd, 17.58 ; water, 12.83 = 100.00. This, as remarked by Mr. Hawes, gives, on cal- 

 culation, an oxygen ratio between protoxyds, sesquioxyds, silica, and water, of 4 : 3 : : 4, very nearly, which 

 puts this mineral, if it be a homogeneous substance (as its microscopic characters would indicate), among the 

 chlorites, some of which it resembles very closely in its atomic ratios. Before the blowpi|)e on charcoal it swells, 

 then fuses quietly into a black globule, giving the usual reactions for copper. The iron is almost wholly in the ■ 

 state of sesquiosyd, as shown by two determinations of the amount of jirotoxyd of iron, which gave, respectively, 

 0.27 and 0.29 per cent. This copper-chlorite appears alike from its physical and chemical characters to constitute 

 a distinct mineral species, for which I propose the name of Venekitiv, in allusion to tlie mythological and alchemis- 

 tic name of copper."— ( "A New Ore of Copper and its jMetallurgy." Trans. Amer. Inst Mining Engineers, iv. 325.) 



The atomic formula for venerite given in the table above represents it as a chlorite in which a part of the 

 sesquioxyd is ferric and a part of the protoxyd is cupric. This formula (mg.„;,jCHi..j5al.i..v)fi(i-jnSiG-oo)On.*i + 4aq., 

 requires silica, 31.4; alumina, 14.8; ferric oxyd, 4.(>; magnesia, 19.2; cupric oxyd, 17.4; water, 12.0 = 100.0, 

 which agrees very closely with the numbers deduced by Hawes from his analysis, and varies but little from my 

 own analysis, given above, of a less pure specimen, when calculated for 100.0 parts. A microscopic examination 

 of this curious chlorite will sufHce to show its distinctness, and the judgment of Hawes thereon is confirmed by 

 that of Bes Cloizeaux, accoi-ding to his private communication to the writer. 



