Geology Rock Garden Guide to the
Rock Samples
Compiled by
CSUS Geology Department
US Geological Survey
Volcanological
Society of Sacramento
- petrified wood
- calcite
- andesite (columnar)
from Lake Tahoe Basin
- opal (hydrothermal
silica deposit)
- medium grained
sandstone with bedding, from the Great Valley Sequence
- flow layered rhyolite
pumice (lava)
- flow layered rhyolite
pumice
- rhyolite obsidian with
bands of pumice
- fine-grained sandstone
with preserved ripple marks
- volcanic tuff (erupted
deposit of pumice and ash)
- medium-grained
hornblende mica granodiorite
- layered obsidian with
flow fold
- complex diorite with a
granite dike (intrusion)
- columnar basalt from
Modoc Plateau
- green volcanic tuff;
pumice, ash and rock fragments from an explosive volcanic eruption near
Barstow
- travertine (hot spring
or hydrothermal deposit) from Bridgeport area
- fused tuff
- volcanic tuff lake-bed
deposit with mudcrack impressions
- tufa limestone; as seen
in Mono Lake
- rhyolite obsidian and
pumice; flow layered
- vesicular basaltic lava
- coarse-grained
conglomerate (river deposit)
- welded Bishop rhyolite
tuff
- serpentinite
(California State Rock)
- serpentinite (with
preserved fault slip)
- obsidian with
breadcrust texture
- an ugly rock
- flow layered rhyolite
obsidian with devitrification spherulites
- fossil-rich gray
sandstone
- melted tuff on pumice
- dacite drill core
sample from the Mehrten Formation, Morman Slab Dam, Folsom Lake
- Boulder size
conglomerate of Mehrten Formation, Morman Slab Dam, Folsom Lake
- Garnet skarn with some
pyrite, malachite and epidote
- Folded hornfel from
Winnemucca, NV
- Volcanic tuff lakebed
deposit with mud crack impressions