21 
forTnation from Montmartre. Rocksalt, consti- room viii. 
tuting a formation nearly related to that of Na ’’ Hist , 
gypsum. 
(Div. 8 .) Containing porphyry, sienite and 
the trapp-formation.—Hornstone porphyry, from 
Scotland, Norway, Thuringia, Egypt, See. 
(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 feldspar in several 
stages of decomposition ; with mica ; (the Sax- 
um 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 Triimmer-porphyr.—Porphyry slate. 
Sienite : (fragment of an Egyptian idol 
composed of much hornblende, reddish feldspar 
unequally distributed, and some mica: the true 
Signites of Pliny) ; similarly grained, without 
mica; with quartz (bianco e nero d’Egitto) ; 
porphyritic sienite consisting chiefly of horn¬ 
blende appearing to pass over into hornblende 
slate.—Common hornblende rock.-—Hornblende 
slate.—Greenstone—Greenstone porphyry : por- 
fido verde antico, or serpentine verde antico, 
as 
