Sapphire
Corundum (Al2O3)
Category
Browse mineral in igneous rock specimens identified by the Rock Identifier community.
Sapphire
Corundum (Al2O3)
Amazonite
KAlSi3O8 (Potassium Feldspar, variety of Microcline)
Black Spinel
Magnesium Aluminum Oxide (MgAl2O4)
Quartz (milky quartz variety)
Quartz (SiO₂)
Pumice
Pumice (a highly vesicular volcanic glass)
Obsidian
Volcanic Glass (SiO2, usually 70% or more)
Basalt
Basalt (Mainly Plagioclase Feldspar and Pyroxene)
Sandstone (Pebble/Cobble)
Sandstone (arenite is a more precise term for sandstone with less than 15% matrix; this specimen appears to be a lithic or quartz arenite)
Quartzite River Rock
Quartzite (primarily SiO2)
Shale
Clastic sedimentary rock (primarily clay and silt minerals)
Sandstone
Sandstone (various mineral compositions)
Quartz Veined Rock (Likely Graywacke or Quartzite)
Silicon Dioxide (SiO2) veins in Metasedimentary matrix
Sandstone
Arenite (SiO2 based with various mineral cements)
Sandstone (specifically Banded Sandstone)
Clastic sedimentary rock (primarily SiO2)
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Sandstone (with Iron Staining)
Clastic Sedimentary Rock (primarily Quartz with Limonite/Goethite staining)
Agate
Agate (Silicon Dioxide, SiO2)
Scoria (Vesicular Basalt)
Scoria (Hydrated silicate volcanic rock with iron and magnesium)
Pumice
Pumice (Amorphous volcanic glass)
Scoria (Lava Rock)
Scoria
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Pumice
Pumiceous rhyolite / Volcanic glass
Quartz (Milky or Rough Variety)
Silicon Dioxide (SiO2)
Agate
Silicon Dioxide (SiO2) - variety Chalcedony
Porphyry
Porphyritic Basalt or Porphyritic Andesite
Plagioclase Feldspar (specifically Albite/Oligoclase)
(Na,Ca)(Si,Al)4O8
Red Jasper
Silicon Dioxide (SiO2) with Hematite inclusions
Citrine
SiO2 (Silicon Dioxide)
Quartz Geode
Silicon Dioxide (SiO2)
Yellow Quartz (Citrine/Yellow Chalcedony)
Silicon Dioxide (SiO2)
Quartz Vein in Host Rock
Silicon Dioxide (SiO2) within Sedimentary/Metamorphic Matrix
Granite Pebble
Phaneritic Felsic Igneous Rock (primarily SiO2, KAlSi3O8, NaAlSi3O8)
Granite
Granite (Phaneritic intrusive igneous rock; primarily SiO2 and Al2O3)
Pink Granite
Phaneritic Plutonic Igneous Rock (high K-feldspar content)
Granite
Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)
Pink Granite
Phaneritic Acidic Igneous Rock (primarily SiO2, Al2O3, K2O)
Granitoid (Granite/Diorite)
Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica/Amphiboles)
Granite (Pink Orthoclase variety)
Phaneritic intrusive igneous rock (Quartz, Orthoclase, Plagioclase, and Mica)
Granite
Phaneritic intrusive igneous rock (composition: Quartz, Feldspar, Mica)
Granite
Phaneritic Felsic Igneous Rock (composed of quartz, feldspar, and mica)
Vesicular Basalt (Scoria)
Mafic extrusive volcanic rock (predominantly Plagioclase feldspar and Pyroxene)
Basalt Porphyry (River Pebble)
Porphyritic Basalt