Mineralogy and Petrography. es 5I 
-this view the plane of their optical axes is the orthopinacoid. 
Their bisectrix i is positive and perpendicular to «Px. 2 E =125°. 
Sot mineral is pleochroic in red and brown tints. Withamite 
porphyrites of Glencoe, County Argyle, Scotland, the 
-same author regards* simply as epidote. He also thinks? that . 
- mismondine, Sasonite, ottrelite, venasquite, and phyllite are merely 
_ Varieties of chloritoid, the, optical properties of which he de- 
pecies. He states also that Dufrenoy’s dréelite i is an 
impure barite.—New analyses of agalmatolite7 indicate that 
Most of the substance to which this name has been given really 
possesses no definite composition, but is probably a mixture of 
silica and hydrated silicates of potassium a and aluminium, re- 
-An a pparently 
H k to the wey law. It is often intergrown with tridymite. 
ogee . ecific gravity = 2.27. Its composition is 
Rath a 91 per cent. Fe,O,.Al,O, = 6.2 per cent. Both Vom 
ing Say Bauer regard it as most probably regularly crystalliz- . 
Shica, It has been called christobalite to distinguish it from 
asmanite, tridymite, vestan (Jensch, Pog. Ann., 1858, p. 320), and 
ite——A new variety of dufrenite has been observed by 
h - Kinch, Butler and Miers in Cornwall, England. When 
it is found in small black or apple-green orthorhombic 
sags in the thin section appear yellow or brown. Its 
'S 4.5 and specific gravity 3.233. An analysis yielded: 
S CuO P,O, Fe,0, CaO 
pe a * 30.42 55:93 1.51 
ee of the mineral corresponds with that of Streng’s 
€ composition of a micaceous mineral from a 
ein in the Kaiserstuhl is recorded by Knop™ as follows: 
Fe,O,  Mn,O M 2 eee 
LIŞ 15.18 10.85 0.89" 2280 20 ror 
EAL Soo Fr. du Min., ix. p. 75- 
3 Ib., p. 78. 
ip 217. 
Seea n. d. Fra viii, 1385p . 428. *Ib.,p. pr 
N he 1886, PP- 24 and 29; hee. 1886, p. 74. 
Min, T an A ype etc., SEa i. p. 198. 
pe Jahrb. f. 
Min, 188m i. p. ror. = Zeits, f. Kryst., xii. p. 607. 
