Weathered quartz-rich granitoid (likely granite or granodiorite)
Granite–granodiorite; chiefly quartz (SiO₂), feldspar, and minor mica/amphibole
igneous
Category
Man Made Material
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Worn quartz-rich pebble, likely chert or quartzite
Microcrystalline quartz (SiO₂), possibly quartzite
sedimentary or metamorphic
Iron-stained quartz-rich rock, possibly quartzite or hydrothermal quartz
Quartz (SiO₂), likely with iron oxides; exact host rock uncertain from the photograph
metamorphic
Veined quartz-bearing metamorphic rock
Likely quartzite or siliceous schist with iron-oxide staining
metamorphic
Weathered porphyritic volcanic rock
Likely altered andesite or rhyolite porphyry
igneous
Olivine
Olivine group (Mg, Fe)2SiO4
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Quartzite
Quartzite (SiO2)
metamorphic
Quartz
Silicon Dioxide (SiO2)
mineral
Peridot (Olivine)
Olivine ((Mg, Fe)2SiO4)
mineral
Slag Glass (Cullet Glass)
Amorphous Silica (Industrial byproduct)
mineral
Red Jasper with Quartz
Silicon Dioxide (SiO2)
sedimentary
Orange chalcedony (likely carnelian), polished shard
Microcrystalline quartz, SiO₂; chalcedony variety, orange iron-oxide coloration
gemstone
Aragonite Star Cluster
Aragonite (CaCO3)
mineral
Slate
Slate (Regional metamorphic rock composed primarily of quartz, illite, and chlorite)
metamorphic
Cubic Zirconia (Set in Jewelry)
Zirconium Dioxide (ZrO2)
gemstone
Sugilite
Sugilite (KNa2(Fe,Mn,Al)2Li3Si12O30)
mineral
Coquina
Biogenic Limestone (Coquina)
sedimentary
Weathered granite or granitic pegmatite cobble
Granite/granitic rock, composed mainly of quartz (SiO₂), feldspar, and minor biotite or other dark minerals; the reddish-brown areas may be iron-oxide staining or weathered accessory minerals
igneous
Diamond
Native Carbon (C)
gemstone
Diamond and Sapphire
Carbon (Diamond, C) and Aluminum Oxide (Sapphire, Al2O3)
gemstone
Rough Diamond
Diamond (Native Carbon, C)
mineral
Diamond
Carbon (C)
mineral
Petrified Wood
Silicified Wood (SiO2)
fossil
Rhodochrosite
Rhodochrosite, Manganese Carbonate (MnCO3)
mineral
Seashell Fossil
Gastropoda fossil
fossil
Diamond
Diamond (pure carbon, C)
mineral
Raw Diamond
Diamond (pure Carbon, C)
mineral
Diamond (set in a gold ring)
Carbon (C) - Adamantine cubic carbon
mineral
Chert (Chert Nodule)
Microcrystalline quartz (SiO2)
sedimentary
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Olivine (Peridot)
Magnesium Iron Silicate (Mg, Fe)2SiO4
mineral
Metallic sulfide ore, likely galena-bearing rock
Galena (lead sulfide, PbS), possibly with pyrite or other sulfides
mineral
Tumbled green aventurine (likely)
Quartz, SiO₂, containing green fuchsite mica or other inclusions
mineral
Rounded quartz-rich pebble
Chert or quartzite pebble (tentative; mostly microcrystalline quartz, SiO₂)
sedimentary
Diamond (Faceted)
Carbon (C)
gemstone
Sandstone (with manganese staining)
Clastic sedimentary rock (primarily SiO2)
sedimentary
Rough Diamond
C (Native Carbon)
gemstone
Diamond
Natural Diamond (Carbon, C)
mineral
Rough Diamond
Diamond (pure Carbon, C)
mineral
Petrified Wood
Silicified Wood (SiO2 permineralization)
fossil
Limonite with Trace Fossils
Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)
sedimentary