United States Quarter Dollar
Cupronickel Clad Alloy (75% Copper, 25% Nickel over a 100% Copper core)
Metal / Man-made mineral-like object
Category
Anthropogenic (Man Made Industrial Deposit)
Browse anthropogenic (man made industrial deposit) specimens identified by the Rock Identifier community.
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Graphite
Graphite (Native Carbon, C)
metamorphic
Goldstone
N/A (Synthetic Glass with Copper Inclusions)
Manufactured Glass
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
sedimentary
Quartz with Hematite Inclusions
Silicon Dioxide (SiO2) with Ferric Oxide (Fe2O3)
mineral
Rhodolite Garnet
Magnesium Aluminum Silicate; formula: (Mg,Fe)3Al2(SiO4)3
mineral
Coquina
Bioclastic Limestone
sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
sedimentary
Pyrite cluster (iron pyrite)
Pyrite, FeS₂
mineral
Coquina
Bioclastic Limestone
sedimentary
Blue-dyed howlite beads (likely)
Howlite, Ca₂B₅SiO₉(OH)₅, commonly dyed blue to imitate turquoise
mineral
Rough Emerald
Beryl (Be3Al2Si6O18 with Chromium/Vanadium impurities)
mineral
Gold-bearing Quartz
Auriferous Quartz (SiO2 with Native Gold inclusion)
mineral
Slag (Industrial By-product)
Glassy silicate or metallic smelting residue
mineral-like (anthropogenic)
Rose Quartz Carving
Quartum roseum (Variety of Quartz, SiO2)
Mineral
Coquina and Oyster Fossil Rock
Coquina limestone (Calcium Carbonate, CaCO3) containing fossilized Crassostrea / bivalve shells
fossil
Turquoise
Turquoise, CuAl6(PO4)4(OH)8·4H2O
mineral
Raw amethyst (purple quartz)
Amethyst; quartz, SiO₂, colored by trace iron and irradiation
mineral
Desert Rose (Gypsum)
Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O
mineral
Diamond in Kimberlite
Diamond (C in Kimberlite Matrix)
igneous
Chert (Flint)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
sedimentary
Pumice
Pumice (Vesicular volcanic glass)
Igneous
Chert
Chert (microcrystalline quartz)
sedimentary
Slag (Industrial Glassy Byproduct)
Ferro-silicate Slag
Anthropogenic / Non-Natural
Chert
Microcrystalline Quartz (SiO2)
sedimentary
Bog Iron / Limonite Concretion
Goethite/Limonite mixture (FeO(OH)·nH2O)
sedimentary
Chert (Flint nodule)
Chert (SiO2)
sedimentary
Calcite (likely honey/orange calcite)
Calcite — calcium carbonate, CaCO₃
mineral
Sandstone (Quartzose)
Arenite (composed primarily of SiO2)
sedimentary
Chert (often called Flint)
Chert (Cryptocrystalline Quartz, SiO2)
sedimentary
Tumbled yellow quartz (likely citrine or iron-stained quartz)
Quartz, SiO₂; yellow color from trace iron or irradiation/heat-related coloration
mineral
Green Aventurine
Quartz (SiO2) with Fuchsite inclusions
Mineral
Chert (Flint)
Chert (Silicon Dioxide, SiO2)
sedimentary
Amethyst
SiO2 (Silicon Dioxide with iron impurities)
mineral
Iron Slag
Vitreous glassy waste (Fe-Si-Al-Ca compounds)
Mineral byproduct (anthropogenic / techno-fossil)
Coquina
Bioclastic Limestone
sedimentary
Flower Agate
Chalcedony (SiO2) with inclusions
mineral
Chert
Microcrystalline Quartz (SiO2)
sedimentary
Milky Quartz
Crystalline Silicon Dioxide (SiO2)
mineral
Pearl-and-gemstone insect brooch
Pearl: nacre (aragonite, CaCO₃); colored stones are likely synthetic or natural corundum/spinel/glass, not determinable from the image
gemstone
Diamond
Carbon (C)
gemstone
Malaysian 50 Sen Coin
Coinage (specific alloy unknown without metallurgical analysis, but typically brass or bronze for this denomination and era)
Man-made object (coin)