Not A Natural Rock (Man Made Composite)

Clear quartz crystal

Quartz (silicon dioxide, SiO₂)

Citrine (Iron-stained Quartz)

Silicon Dioxide (SiO2)

Schist

Crystalline Metamorphic Rock (Schistose)

Granite

Phaneritic Plutonic Felsic Rock (Granite)

Pink Granite

Phaneritic Felsic Igneous Rock (Granite)

Iron-stained sandstone or weathered ironstone concretion

Quartz-rich sandstone, locally cemented by iron oxides (hematite/goethite); exact identification requires testing

Picture Jasper

Silicon dioxide (SiO2)

Rounded gray stone, likely slate or fine-grained sandstone

Probable slate (low-grade metamorphosed shale) or lithic sandstone; exact identification requires testing

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Aventurine

Silicon Dioxide (SiO2) with inclusions of Fuchsite mica

Yellow calcite crystal cluster with calcite fragment

Calcite, calcium carbonate (CaCO₃)

Chalk

CaCO3 (primarily Calcium Carbonate), biogenic sedimentary rock

River Pebble (Sandstone / Quartzite)

Sedimentary rock (Quartz arenite / Quartzite pebble)

Granite

Granite (Phaneritic intrusive igneous rock)

Sandstone

Sedimentary Rock (Quartz Arenite)

Agate Geode

Microcrystalline Quartz (SiO2)

Brown chalcedony (likely carnelian/iron-stained quartz)

Microcrystalline quartz, SiO₂; brown coloration from iron oxides/hydroxides

Asphalt (Bituminous Rock)

Natural bitumen or Bituminous limestone/sandstone

Smoky Quartz with Siderite

Silicon Dioxide (SiO2) with Iron(II) Carbonate (FeCO3)

Basalt Pebble (River Rock / Beach Stone)

Basalt (fine-grained mafic igneous rock)

Moss-covered Rock Fragment

Weathered Rock Fragment with Epilithic Growth

Quartz (likely Herkimer Diamond style)

Silicon Dioxide (SiO2)

Likely foliated metamorphic rock, possibly schist

Mica schist or micaceous quartzite; exact identification is uncertain from the photograph

Rounded river or beach pebble

Likely quartz-rich sandstone or quartzite; exact identification requires a close-grained view and hardness test

Shale

Shale (clay-sized silicate minerals)

Sandstone

Arenite (SiO2 based)

Yellow Quartz (Citrine Quartz variety / Ferruginous Quartz)

Silicon Dioxide (SiO2) with iron inclusions

Dark volcanic sand / basaltic sand

Basalt-derived lithic sand, chiefly plagioclase, pyroxene, and volcanic glass

Tumbled granite

Granite, chiefly quartz, feldspar, and mica

Limonite / Goethite (Ironstone Nodule)

Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)·nH2O)

Sandstone (Ferruginous)

Ferruginous Sandstone (SiO2 with Fe2O3/FeO(OH) cement)

Weathered metallic-looking rock, possibly hematite-bearing ironstone

Hematite-rich ironstone; hematite Fe₂O₃, potentially with magnetite Fe₃O₄ and quartz

Rounded brown-gray stone, possibly weathered conglomerate or sandstone

Indeterminate clastic sedimentary rock; likely poorly cemented sandstone/conglomerate

Basalt Pebble

Extrusive mafic igneous rock

Pink Granite

Phaneritic Felsic Igneous Rock

Diorite (Salt and Pepper Rock)

Diorite

Sandstone (Quartzose)

Arenite (composed primarily of SiO2)

Green Aventurine

Silicon Dioxide (SiO2) with Chromium-bearing Fuchsite

Slate

Slate (Metamorphic Rock)

Weathered porphyritic volcanic rock (likely andesite or basalt)

Aphanitic to porphyritic andesite–basalt; composition commonly plagioclase, pyroxene, and minor iron oxides

Yellow Quartz (Citrine / Milky Quartz)

Silicon Dioxide (SiO2)

Chalcopyrite (Peacock Ore)

Chalcopyrite (CuFeS2)