1885.] NATURAL SCIENCES OF PHILADELPHIA. 121 



found at the Wheatley lead mines, south of I'lmnixville. It 

 occurs here in veins and incrustations of a beautiful rose-pink 

 color. Under the microscope these incrustations are shown to be 

 for the most part composed of minute globular rosettes of crys- 

 tals, while earthy and fibrous masses also occur. The mineral 

 was found to fuse easily in the name of a Bunsen burner, coloring 

 the flame pale grayish blue, the color of burning arsenic. A borax 

 bead was colored deep blue, proving the presence of cobalt. The 

 erythrite was associated with fluorite and blende. The speci- 

 mens were collected by Mr. L. Woolman. 



Genthite. — Genthite, a hydrous silicate of nickel and magnesia, 

 was discovered in emerald-green coatings on the Schuylkill Valley 

 Railroad, about a hundred feet north of the steatite quarry at 

 Lafayette, just outside the city limits. It occurs on an actino- 

 lite rock in thin coatings, which, under the microscope, show the 

 mammillary and stalactitic structure characteristic of genthite. 

 Fused with borax, it gives a bead which is violet-brown in the 

 oxidizing flame, and in the reducing flame is reduced to gray 

 metallic particles, these reactions being characteristic of nickel. 

 The genthite is associated with the numerous magnesian minerals 

 which have made the steatite quarry so well known. Efflores- 

 cences of epsomite and veins of asbestos were found within a few 

 feet of the genthite. 



The discovery of genthite has a geological interest in demon- 

 strating the presence of nickel in the serpentine belt which here 

 crosses the Schuylkill. Some years ago Mr. T. D. Rand 1 had 

 found a single specimen of millerite, another nickel mineral, in 

 capillary crystals in the dolomite at the same locality. With this 

 exception, nickel had not been known in this serpentine belt. 

 Chromic iron and other chromium minerals are, however known 

 to occur in several localities in the same zone of serpentine, and 

 the association of chromium and nickel is well known. The ser- 

 pentines of Cornwall, the Alps, the Yosges, and of hundreds of 

 other localities, contain both chromium and nickel. Dr. T. Sterry 

 Hunt states 2 that the serpentines of his third (Green Mountain) 

 series, which he refers to the lower Silurian age, are " marked by 

 the almost constant presence of small portions of the oxides of 

 chrome and nickel," a character which distinguishes them from 

 the serpentines of the Laurentian series, which are usually free 

 from these metals. Dr. Hunt, however, fails to identify the ser- 

 pentine and steatite of Lafayette with his Green Mountain series, 

 but supposes it to belong to another horizon,' refusing to believe 

 that it was derived from an eruptive rock. 



1 Proc. Min. and Geol. Sec. Acad. Nat. Sci. Phila., 1877. 



2 Chemical and Geological Essays, 187o, p. -'>2. 



8 The Geological History of Serpentines. Trans. Roy. Soc. Canada, 

 1883, i, p. 171. 



