1889.] Muter alogy and Petrography. 159 
of calcite in gneiss, which vein has been worked for graphite. 
These pyroxenes are sometimes eighteen inches in length and 
thirty-six inches in circumference, and exhibit a parting paral- 
lel to oP. The pyroxenes are thought to be older than the 
calcite but younger than the quartz with which they are associ- 
ated. — Interesting parallel growths Qiandahisite and sillimanite 
are described and figured by Lacroix* from Ceylon and from a 
metamorphic rock from Morlaix, Finistere, France. In the 
former instance the two minerals are intergrown with their c 
axes parallel, and in addition two other series of sillimanite 
crystals cross the principal one at angles of 90^? and 45''. The 
same author finds that batnlite, monrolite, bucholzite, xenolite and 
wort/lite are either merely peculiar forms of sillimanite or im- 
pure varieties of this mineral. — Two barium feldspars from the 
manganese mines of Sojgrufran, Grythyttan, Sweden have been 
analyzed by Iglestrom.^ The first is a red mineral and the 
second is white and transparent. Both are insoluble in acids. 
Their analyses yielded : 
SiO, ALO. FeO MnOBaO MgO CaO Na.O K„0 
Redfeldspar 61.90 15.80 5.OO 958 1-30 .40 6.02 
Whuefeldspar 54,15 29.60 1. 26 1. 52 I .OO I2.47 
According to Des Cloizeaux the white mineral has the op- 
tical properties of albite.— The same mineralogist records the 
analysis of a clear straw yellow pyrrhoarsenite' from the same 
mine. Its composition corresponds to the formula 10 (Ca. 
Mg. Mn.), (AsO,), -h Ca, Sb,0., and is: 
A0,0, Sb,0, CaO Mno MgO 
5323 6.54 20.21 10.82 920 
Gonnard' mentions the rare mineral /^rZ^^r;///^ as occurring 
in quartz veins cutting granite in the neighborhood of Char- 
bonnieres les Varennes, Fuy-de-D6me, France. Here are 
found also fine pseudomorphs of quartz after calcite, the forma- 
tion of which is explained as having taken place in three stages. 
I), by the coating of the calcite crystals by silica; 2), by solution 
of the calcite, and 3), the filling of the molds left with silicious 
material mixed with a little clay. Druses of smoky quartz 
crystals found in the same veins are thought to owe their color 
to bituminous matter which floated on the surface of the silice- 
ous waters that yielded the quartz and colored those last formed 
(the druse crystals). 
