20 
.room viii. formation from Montmartre. Rocksalt, consti- 
-- > » 
Nat. Hist, tuiing a formation nearly related to that of 
gypsum. 
(Div. 8.) Containing porphyry, sienite and 
the trapp formation.—Hornstone porphyry, from 
Scotland, Norway, Thuringia, Egypt, &c. 
(Egyptian antique porphyry with reddish grains 
of feldspar); porphyry with hornblende, with 
quartz veins; variety with its base less hard, being 
the jasper porphyry of some mineralogists : feld¬ 
spar porphyry from Frauenstein. Clay por¬ 
phyry ; the same, with the feldspaf in several 
stages of decomposition; with mica (the Sa- 
min metalliferum of Baron Born, being the 
principal repository of gold and silver ores 
in Lower Hungary and Transylvania): pitch- 
stone porphyry ; porphyry balls; porphyry 
breccia or Trummer-porphyry.—Porphyry slate. 
Sienite: (fragment of air Egyptian idol, 
composed of much hornblende, reddish feldspar 
unequally distributed, and some mica : being the 
true Signites of Pliny); similarly grained, without 
mica ; with quartz ( bianco e nero d' Egit to) : 
porphyritic sienite consisting chiefly of horn¬ 
blende appearing to pass over into hornblende 
slate.—Common hornblende rock.—Hornblende 
slate.—Greenstone.—Greenstone porphyry: por- 
jido verde antico, or serpentina verde antico-, 
as 
