Chert (or Jasper)
Microcrystalline Quartz (SiO2)
sedimentary
Category
Non Geological
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Quartzite Arrowhead (Archaeological Lithic)
Recrystallized Quartz (SiO2)
metamorphic
Mixed Rock Collection
Polylithic Geological Specimen Mix
sedimentary and igneous
Quartzite
Quartzite (composed primarily of SiO2)
metamorphic
Obsidian / Chert (Arrowhead Artifact)
Obsidian (volcanic glass, SiO2 with impurities)
igneous
Quartzite Pebble
Quartzite (SiO2)
metamorphic
Obsidian
Volcanic Glass (Mainly SiO2)
igneous
Obsidian
Volcanic Glass (High silica amorphous rock)
igneous
Quartzite River Rock
Quartzite (SiO2)
metamorphic
Obsidian
Volcanic Glass (70% or more SiO2)
igneous
Coal (Anthracite)
Anthracite coal (Carbon C)
sedimentary
Obsidian
Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)
igneous
Amber in Matrix
Succinite (Carbon-based organic polymer)
Organic (Sedimentary context)
Moldavite
Tektite (Impact Glass), ~80% SiO2 + Al2O3
tektite
Pink Quartzite
Quartzite (SiO2)
metamorphic
Quartzite (River Stone)
Quartzite (SiO2)
metamorphic
Opal (in Jewelry Setting)
Hydrated Silicon Dioxide (SiO2·nH2O)
gemstone
Rose Quartz
Silicon Dioxide (SiO2)
mineral
Goethite
Goethite (α-FeO(OH))
Mineral
Greenstone / altered mafic rock
Likely chlorite–actinolite metabasalt (greenschist); exact identification requires testing
metamorphic
Gneiss Pebble
Gneiss
metamorphic
Quartzite pebble
Quartzite (SiO2 with trace iron/feldspar)
metamorphic
Black Garnet (Melanite)
Andradite, Ca3Fe2(SiO4)3
mineral
Red Jasper
Chalcedony with Iron Oxide (SiO2)
sedimentary
Green Quartz (including Prase or Aventurine variants)
Silicon Dioxide (SiO2) with inclusions (likely Actinolite or Chlorite)
mineral
Black Jasper (Black Onyx substitute)
Silicon Dioxide (SiO2) with carbonaceous impurities
sedimentary (microcrystalline quartz)
Serpentine (Nephrite-like Serpentine)
Serpentinite (Hydrous magnesium iron phyllosilicate)
metamorphic
Rough Emerald Crystals
Beryl (Be3Al2Si6O18) with Chromium/Vanadium impurities
mineral
Laterite
Laterite (no specific mineral formula as it's a rock type)
Sedimentary
Moldavite
Moldavite (Siliceous vitreous substance)
tektite (natural glass)
Red Coral
Corallium rubrum (for precious red coral), although other species like Corallium japonicum and Paracorallium are also used.
Organic Gemstone (not a rock or mineral in the traditional sense, but bio-mineralized material)
Quartzite Pebble
Metamorphosed Quartz Arenite (SiO2)
metamorphic
Black Obsidian
Obsidian (Volcanic Glass)
igneous
Quartzite Pebble
Quartzite (SiO2)
metamorphic
Quartzite Pebble
Quartzite (SiO2)
metamorphic
Quartzite
Quartzite
metamorphic
Obsidian
Obsidian (Volcanic Glass, ~70% SiO2)
igneous
Obsidian
Vitreous volcanic silicate (70-75% SiO2)
igneous
Orange Crackle Quartz
Silicon Dioxide (SiO2) with thermal fracturing
mineral
Gossan (Limonite/Ironstone)
Hydrated Iron Oxide (FeO(OH)·nH2O)
sedimentary
Aqua Aura Quartz
Titanium/Gold-coated Silicon Dioxide (SiO2)
mineral
Coarse-grained Granite
Granitoid (Felsic Plutonic Rock)
igneous