53 
tutiiig a formation nearly related to that of room viil 
gypsum. NatTh^t. 
(Shelves 5 and 6.) Porphyry.—Hornstone por- cases 
phyry, from Scotland, Norway, Thuringia, Egypt, 7 and 8. 
&c. (Egyptian antiqueporphyry 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, w'ith the feldspar in several 
stages of decomposition; with mica (the Sa- 
xum metalliferum of Baron Born, being the 
principal repository of gold and silver ores 
in , Lower Hungary and Transylvania) : pitch- 
stone porphyry ; porphyry balls ; porphyry brec¬ 
cia or Triimmer-porphyry.—Porphyry slate. 
(Shelves 5 and 6.) Sienite: (fragment of an case 
E gyptian idol, composed of much hornblende, 8. 
feldspar unequally distributed, and some mica : 
being the true signites of Pliny'; similar variety, 
but without mica ; with quartz (bianco e nero 
dlEgltto): porphyritic sienite consisting chiefly 
of hornblende appearing to pass into hornblende 
slate.—Common hornblende rock.—Hornblende 
slate.—Greenstone.—Greenstone porphyry : por- 
Jido verde antico, or serpentmo verde antico, 
as it is sometimes erroneously called.—Basalt, 
N • with 
