White Opal
Hydrated Silica (SiO2·nH2O)
Category
Browse mineraloid (man made origin) specimens identified by the Rock Identifier community.
White Opal
Hydrated Silica (SiO2·nH2O)
Brecciated Jasper or Agatized Dinosaur Bone
SiO2
Pink Aragonite
CaCO3
Blue slag glass or dyed glass-like industrial material
Amorphous silicate glass; likely copper-bearing blue slag, but possibly colored man-made glass
Chondrite Meteorite
Stony Meteorite (Ordinary Chondrite)
Smoky Quartz
Silicon dioxide (SiO2)
Obsidian
Volcanic Glass (Amorphous SiO2)
Obsidian
Volcanic Glass (SiO2 rich)
Polished mahogany obsidian (probable)
Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite
Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Fulgurite
Fulgurite (Lechatelierite-rich fused silica)
Ruby
Corundum (Al2O3 with Chromium traces)
Common opal in iron-stained host rock
Opal (hydrated amorphous silica, SiO₂·nH₂O), likely common opal
Pearl
Calcium Carbonate (Aragonite) with Conchiolin; formula: CaCO3
Limonite/Goethite on Shale
Hydrous ferric oxides (FeO(OH)·nH2O) often associated with argillaceous rock
Fired Clay Brick (Anthropic Rock substitute)
Anthropogenic polycrystalline ceramic (predominantly Mullite and Quartz: Al6Si2O13 + SiO2)
Shungite
Shungite (carbon-rich Precambrian mineraloid)
Granite or Pegmatite in host rock
Granitoid / Felsic Intrusive Rock
Obsidian
Volcanic Glass (70% or more SiO2)
Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with impurities)
Amber in Matrix
Succinite (Carbon-based organic polymer)
Obsidian
Obsidian (Amorphous volcanic glass, predominantly SiO2)
Obsidian
Volcanic glass
Shungite
Carbon-rich mineraloid (Amorphous carbon)
Amber with Inclusion
Succiniferous fossil resin (C10H16O)
Seashell fragment
Calcium carbonate (CaCO3)
Native Silver
Silver (elemental Ag)
Precious Opal
Hydrated Silica (SiO2·nH2O)
Limonite/Ironstone
Limonite (FeO(OH)·nH2O)
Green Opal
Hydrated Silica (SiO2·nH2O)
Rounded gray-green beach cobble
Unidentified lithic cobble; exact rock type cannot be determined from the image
Nickel coin (U.S. currency)
Cupronickel (75% Copper, 25% Nickel alloy)
Black Obsidian
Obsidian (Volcanic Glass, SiO2 + impurity)
Limonite (Iron Ore)
Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)
Likely obsidian (possibly tektite or slag glass)
Volcanic glass; primarily SiO₂, noncrystalline
Obsidian
Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)
Sea Glass (Frosted Glass)
Amorphous Silica (SiO2) with various additives
Polished blue calcite sphere (tentative identification)
Calcite, CaCO₃; blue color generally results from trace impurities or inclusions
Chalcedony (or a variety of Chalcedony, likely Agate or Jasper)
Chalcedony (SiO₂)
Obsidian (black volcanic glass), possibly slag or basalt
Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition
Opal
Hydrated Silica (SiO2·nH2O)
Limonite (Ironstone)
Limonite (mixture of hydrated iron(III) oxide-hydroxides)