1887] ` Mineralogy and Petrography. 473 
ai eon color on the walls of cavities and cracks. 
(e) 
— 
et 
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5 
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= 
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O 
[e$] 
5 
jon 
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e g 
m 
5 
ea 
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ina CE tube gives off 
water and sulphuric acid. Its composition is 
SO, = 30.18, P,O, = 2.72, Fe,O, = 48.52, H,O = 18 48. 
——RIn the same journal Gonnard? ene pleromorphs of 
quartz after fluorite. Curious blocks of milky quartz from St. 
but more frequently a piece of granite or a core of amorphous 
silica. Scattered through the blocks are found cavities of octa- 
hedral form, normal to the faces of which the quartz-fibres are 
arranged. Inside of the cavities are also occasionally little octa- 
hedrons of quartz with their faces parallel to the walls of the 
cavity. Several doubtful minerals have recently been exam- 
ined microscopically Lacroix.2 /terolite, which Dana 
supposed to be an altered lepidomelane, Lacroix found to be a 
mixture of several distinct minerals, of which the most impor- 
tant are a black mica anda strongly pleochroic pyroxene. In 
any other minerals which are usually found in eleolite syenites. 
Villarsite is shown to be merely a pseudomorph of chrysotile 
after olivine. Gamsigradite has the optical properties of horn- 
„blende, with a maximum extinction of 30° and pleochroism in 
rahedrite. He also describes hexagonal plates of ver which 
he thinks are orthorhombic crystals bounded by the planes 
OP, œP% and oP. ‘They are found in the clefts and druses of 
a quartz vein occurring on the contact between a lithium-mica 
_ granite and*a mica schist at the cde. Mine , Joachimsthal. 
connection with his work on mineral veins the same 
author? had occasion to examine the mica of the Schapbach 
gneisses and the augite of a diabase from near Andreasberg, 
Harz. In each he found a silver content of about 0.001 per 
z Comptes PR ciii., 1886, p. 1036. 2 Ib., civ., 1887, p: 97. 
3 Neues Jahrb. f. Min., etc., 1887, i. P- 95- + Ib., p. ITE 
VOL. XXI.—NO. 5. 32 
