Anthropogenic (Man Made Material Processed By Nature)

Sandstone

Quartz Arenite (a common type of sandstone, given the appearance), Arkose, Greywacke (depending on mineralogy)

Bog Iron / Limonite Concretion

Goethite/Limonite mixture (FeO(OH)·nH2O)

Clear quartz crystal

Quartz (silicon dioxide, SiO₂)

Red Sandstone

Arenite (Ferruginous Sandstone)

Red Sandstone

Arenite (predominantly Quartz with Hematite cementation)

Diamond

Diamond (C)

Sandstone (Ferruginous)

Sandstone (Clastic sedimentary rock, predominantly SiO2 with Fe2O3 cement)

Diamond (set in a gold ring)

Carbon (C) - Adamantine cubic carbon

Sandstone (Quartzose Sandstone)

Clastic sedimentary rock (primarily SiO2)

Iron Meteorite

Iron Meteorite (primarily Kamacite and Taenite, Fe-Ni alloys)

Sandstone

Sandstone (SiO2-rich detrital sedimentary rock)

Polished orbicular jasper (likely ocean jasper)

Silicified microcrystalline quartz/chalcedony (SiO₂), with iron-oxide and other mineral inclusions

Diamond and Sapphire

Carbon (Diamond, C) and Aluminum Oxide (Sapphire, Al2O3)

Diamond

Carbon (C)

Diamond

Native Carbon (C)

Basalt with Quartz/Feldspar Inclusions

Amygdaloidal or Porphyritic Mafic Volcanic Rock with Siliceous Veining

Diamond

Carbon (C)

Diamond (or Diamond Simulant)

Carbon (C) - Native Element

Sandstone (Quartzose)

Arenite (primarily SiO2)

Fossiliferous Limestone

Calcium Carbonate (CaCO3) with Bioclasts

Banded malachite cabochon

Malachite, Cu₂CO₃(OH)₂; the dark bands may be manganese-oxide or other sulfide-rich matrix, and could also indicate a composite or treated specimen

Uncertain polymict breccia or altered volcanic rock

Likely hydrothermally altered volcanic breccia; exact mineral identification requires testing

Sandstone

Arenite (SiO2 primarily)

Limestone

Calcium Carbonate (CaCO3)

Diamond

Diamond (Carbon, C)

Sandstone

Sandstone (clastic sedimentary rock composite)

Diamond

Carbon (C)

Vesicular Basalt (Iron Scoria)

Aphanitic Mafic Igneous Rock with Vesicular Texture

Greenstone / Epidosite

Epidosite (Metasomatic rock consisting mainly of Epidite Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH) and Quartz)

Schist

Mica Schist (primarily consisting of muscovite, biotite, and quartz)

Polished/tumbled jasper, likely ocean jasper or brecciated jasper

Jasper: microcrystalline quartz (SiO₂) with iron oxides and other silicate impurities

Limonite (Ironstone Concretion)

Limonite (FeO(OH)·nH2O)

Diamond (Macled/Crystal fragment)

Carbon (C), isometric crystal system

Quartzite Pebble

Metamorphic Quartz (SiO2)

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Granite

Phaneritic Felsic Igneous Rock

Diamond

Carbon (C)

Limestone

Calcium Carbonate (CaCO3)

Quartz

Silicon Dioxide (SiO2)

White calcite (likely tumbled calcite or marble fragment)

Calcite, calcium carbonate (CaCO₃); if the specimen is granular and rock-like, it may be marble, a calcite-rich metamorphic rock

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

Mixed river gravel (alluvial conglomeratic sediment)

Polymictic alluvium; composition includes quartz, feldspar, chert, granite, basalt, and metamorphic rock fragments