Part 58 (2/2)

SCORIae. _Syn._ volcanic cinders; reddish brown or black porous form of lava. _See_ p. 373.

SERPENTINE. A greenish rock, in which there is much magnesia; usually contains diallage, which is nearly allied to the simple mineral called serpentine. Occurs sometimes, though rarely, in dikes, altering the contiguous strata; is indifferently a member of the trappean or hypogene series.

SYENITIC-GREENSTONE; composition, crystals or grains of felspar and hornblende. _See_ p. 372.

TEPHRINE, synonymous with lava. Name proposed by Alex. Brongniart.

TOADSTONE. A local name in Derbys.h.i.+re for a kind of wacke, which see.

TRACHYTE. Chiefly composed of gla.s.sy felspar, with crystals of gla.s.sy felspar. _See_ p. 372.

TRAP TUFF. _See_ p. 374.

TRa.s.s. A kind of tuff or mud poured out by lake craters during eruptions; common in the Eifel, in Germany.

TUFACEOUS CONGLOMERATE. _See_ p. 374.

TUFF. _Syn._ Trap-tuff, volcanic tuff. _See_ p. 374.

VITREOUS LAVA. _See_ Pitchstone and Obsidian.

VOLCANIC TUFF. _See_ p. 374.

WACKe. A soft and earthy variety of trap, having an argillaceous aspect. It resembles indurated clay, and when scratched exhibits a s.h.i.+ning streak.

WHINSTONE. A Scotch provincial term for greenstone and other hard trap rocks.

a.n.a.lYSIS OF MINERALS MOST ABUNDANT IN THE VOLCANIC AND HYPOGENE ROCKS.

Silica. Alu- Mag- Lime. Pot- Soda. Iron. Manga- Remain- mina. nesia. ash. Oxide. nese. der.

Actinolite 64 -- 22 -- -- -- 3 a 4305 C.

(Bergman) trace

Albite (Rose) 6884 2053 -- a trace -- 912 -- -- -- --(mean of 4 6945 1944 013 022 -- 995 a -- -- a.n.a.lyses) trace

Augite (Rose) 5336 -- 499 2219 -- -- 1738 009 -- --(mean of 4 5357 1 1126 209 -- -- 1075 067 -- a.n.a.lyses)

Carbonate of -- -- -- 5633 -- -- -- -- -- Lime (Biot)

Chiastolite 6849 3017 412 -- -- -- 27 -- 027 W.

(Landgrabe)

Chlorite 26 185 8 -- -- 2 43 -- -- (Vauquelin) --(mean of 3 2743 179 1456 050 156 -- 3063 -- 692 W.

a.n.a.lyses)

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