362 _ The American Naturalist. [April, 
Saati of the three groups may be peeenenics by the following 
analyses 
SiO, Al,O, FeO; FeQ CaO MgO K,O Na,O Loss Sp. Gr. 
te fee e 6 e825 Bek gi 1.6 2.60 
(2) 44:2 10.8 Poe 8 Oo aL 69: LS 2608 
(7) Oe iki 3 bl 8 a ee a -9 2.645 
Wethered 8 has examined the Jurassic pisolite of Cheltenham, 
England, and has discovered to his surprise that its structure is not 
concretionary, but that it is of organic origin. The spherules showa 
nucleus, surrounded by numerous concentric layers of innumerable 
minute tubuli, produced by an organism similar to Girvanella. 
The Kentish Rag, from near Maidstone, Eng., contains a large pro- 
portion of calcium sulphide, as shown by an analysis made by Mr. 
Sanford: ° 
S0, FeO, AlO RO, CaO MgO Alk CO SO, CaS: “Aq 
72.051 2.15 S055 22-625 E 392 9-984 647 1.334 -995 
——Some of the peculiarities of the numerous dykes cutting the slates 
and granite in the neighborhood of Kennebunkport, Maine, are men- 
tioned by Mr. Kemp.” The rocks forming the dykes are granites, 
diabases, camptonites, and diabase porphyrites. 


New Minerals. — Redingtonite, knoxvillite, metastibuite and 
nopalite.— At the hundred and fifty foot level of the Redington 
Mine, in the Knoxville District, California, is a hydrous chromium 
sulphate, supposed to be the result of the action of solfataric gases 
of a pale purple color, that becomes colorless in the thin section. 
The fibres are doubly refractive, and have an extinction varying 
between 13° and 38°. When heated, the mineral turns green without 
losing all of its water, and then agrees in most of its properties 
with copiapite. The green sulphate consists of rhombic tables with 
angles of 78° and 120°. They have good cleavages parallel to the 
base, the prismatic faces and the macropinacoid. The absorption is 
greatest when the short diagonal of the crystals corresponds with the 
principal plane of the nicol. The axes ‘of elasticity lie.in the oP 
face—the one parallel to the brachy-axis being the greater. Mr. 
Becker" calls the purple mineral redingtonite and the green one 
8 Geol. Magazine, May, 1889, p. 197. 
9 Ib. Feb., 1889, p. 
10 Amer. Sonlanie; Mar. 1890, p 
1 G. F. Becker; Geology of the Oua Deposits of the Pacific Slope. Mono- 
graphs XIII. Washington, 1888, p. 343. 
