. Transactions. tin No. 597 (1917) 257. 44 L. C. Graton and Joseph Murdoch: Op. 51. 45 G. F. Becker and A. L. Day: Op. cit., 284. 46 F. L. Ransome: The Ore Deposits of the Rico Mountains, Colorado. U. Survey, 22nd Annual Report, Pt. 2, 279, and plate XXXV. 22 MECHANICS OF VEIN FORMATION for its accumulation, and concludes that the growth of the quartz layerswas continuous during the period of reef Lenticular form is characteristic of most aggregations of mineral mat-ter that develop in highly laminated rocks, such as shales or schists, anddisplace rather than re
. Transactions. tin No. 597 (1917) 257. 44 L. C. Graton and Joseph Murdoch: Op. 51. 45 G. F. Becker and A. L. Day: Op. cit., 284. 46 F. L. Ransome: The Ore Deposits of the Rico Mountains, Colorado. U. Survey, 22nd Annual Report, Pt. 2, 279, and plate XXXV. 22 MECHANICS OF VEIN FORMATION for its accumulation, and concludes that the growth of the quartz layerswas continuous during the period of reef Lenticular form is characteristic of most aggregations of mineral mat-ter that develop in highly laminated rocks, such as shales or schists, anddisplace rather than replace the older minerals. Eye-like lenses mayresult from the growth of a single crystal, in which case the outer cir-cumference of the lenses is filled in with other minerals, as in Fig. 3. Thesingle crystal may be of such mineral as garnet, biotite, pyrite, galena, orsphalerite, while the remainder of the lens is filled with quartz or lenses are formed by the growth of crystalline aggregates. The. Inch Fig. 3.—Sketch showing eye-like lens in quartz mica schist. The layersof mica have been displaced by the growth of the pyrite crystal whilequartz has been largely removed from points of greatest pressure and re-deposited where the pressure was least. calcareous concretions shown in Fig. 4 are essentially similar to the gold-quartz lenses shown in Fig. 5, and in both cases the form has obviouslyresulted from similar processes. In a previous publication,48 the writerhas cited the lenticular form of certain auriferous-quartz veins as evidencethat the vein minerals had made room for themselves by forcing the wallsapart. One of these veins, exposed in the Tellurium mine, Virginia,consisted of lenses which were in some cases wonderfully symmetrical inform. In laboratory experiments, lenticular veins were obtained throughthe slow growth of crystalline masses of salts between layers of heavycardboard coated with parafnne. 47 E. J. Dunn: Reports on the B
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