PERIDOTITE (DUNITE), IG-90A. |
Washington. Green to greenish gray,
medium to very coarse grained, near
PERIDOTITE (HARZBURGITE), IG-90B.
Montana. Medium grained, ultramafic rock
composed of dark green enstatite and yellow-
green olivine. Limited stock
PERLITE, IG-95. Arizona. Light gray
with some spherulites and ejecta.
PHONOLITE Check for availability of all phonolites.
PUMICE, IG-105. California. Light
gray. Sometimes referred to as feather stone.
PUMICE, IG-105A. California. Nearly
white. Appearance of tuff to naked eye. Very
buoyant in water.
QUARTZ DIORITE, see under DIORITE
QUARTZ LATITE, see under RHYODACITE
QUARTZ MONZONITE, see under ADAMELLITE
RHYOLITE, IG-115. California.
Aphanitic. Light shades of green, greenish gray
with widely scattered 1-3 mm grains
mafic minerals and quartz. Up to 2 cm euhedral
phenocrysts of white alkali feldspar
RHYOLITE PORPHYRY, IG-115A.
California. with 5-10 mm euhedral
quartz and 1-2 mm mafics in light gray to
brownish aphanitic groundmass.
RHYOLITE, IG-115B. Colorado.
Light pink to pinkish brown. Widely scattered
grains of feldspar and biotite. Castle Rock
Rhyolite caps some mesas near Castle Rock and is quarried as building stone;
it was erupted as a glowing cloud of hot volcanic ash 35 million years ago
from a former volcano in the Sawatch Range, probably near present Mount
Aetna north of Monarch Pass.
RHYOLITE, IG-115C. Cost A. Nevada.
Gray-brown, aphanitic, I mm or less scattered
vesicles, roughly parallel white flow structure
RHYOLITE, IG-115D. Nevada.
Light gray-beige to reddish brown, aphanitic,
scattered 1-2 mm grains glassy quartz and biotite mica. Pronounced flow structure banding.
RHYOLITE BRECCIA, IG-115E.
RHYOLITE BRECCIA, IG-115F.
California. Gray, brownish or reddish aphanitic
brecciated rhyolite fragments to 3 cm and
scattered 1-3 mm glassy feldspar in purplish
Nevada. Spectacular. Rhyolite fragments in
pastel shades of off-white, blue, gray, brown,
pink, lavender, etc. Cemented fragments
average 3-6 mm, but larger and smaller usually
present. Currently available.
RHYOLITE, IG-115G. Cost A. California.
Porphyritic, slightly vesicular, 1-2 mm feldspar
crystals, red-brown groundmass.
SCORIA, IG-120. California. Dark
gray glass scoria.
SCORIA, IG-120A. California.
Reddish brown to black basalt scoria.