Man Made Material (Anthropogenic 'Mineraloid')

Sandstone (Pebble/Cobble)

Sandstone (arenite is a more precise term for sandstone with less than 15% matrix; this specimen appears to be a lithic or quartz arenite)

Obsidian

Volcanic glass (SiO2 - Silicon Dioxide with impurities)

Gneiss

Gneiss (a type of metamorphic rock)

Quartz (Float/Abraded)

Quartz (SiO₂)

Peridot

Olivine (specifically, the gem-quality variety forsterite, (Mg,Fe)2SiO4)

Quartz

Quartz (SiO2)

Granite

Granite (a common rock type, not a single mineral; composed primarily of Quartz, Feldspar (Orthoclase and Plagioclase), and Mica (Biotite and/or Muscovite) and/or Amphibole)

Cockle Shell (Fossil or Recent)

Class Bivalvia, Family Cardiidae (e.g., Cerastoderma edule for common cockle)

Pearl

Calcium Carbonate (Aragonite) with Conchiolin; formula: CaCO3

Quartz

SiO₂ (Silicon Dioxide)

Citrine Quartz

Citrine (Silicon Dioxide - SiO2)

Quartz

Quartz (SiO₂)

Quartz (likely tumbled or naturally water-worn)

Quartz (SiO₂ - Silicon Dioxide)

Granite

Granite (a common rock name, not a single mineral species, composed primarily of quartz, feldspar, and mica/amphibole)

Quartz

Quartz (SiO₂)

Granite

Granite (Felsic intrusive igneous rock)

Limonite (Yellow Ochre)

Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)

Sandstone

Quartz Arenite (a type of sandstone composed of more than 90% quartz)

Green Calcite

Calcite (CaCO3)

Diamond

Diamond (C)

Chert (Flint)

Chert (microcrystalline quartz)

Quartzite

Quartzite (primarily SiO2)

Slate

Slate (a fine-grained, foliated metamorphic rock). Mineral composition: Primarily composed of mica minerals (muscovite, chlorite, sericite) and quartz, with minor amounts of hematite, pyrite, and other accessory minerals.

White Precious Opal

Hydrated Silica (SiO2·nH2O)

Quartz (likely)

Quartz (SiO2 - Silicon Dioxide)

Obsidian

Volcanic glass (high silica volcanic rock)

Calcite

Calcite (CaCO3)

Pearl

Organic Mineraloid (CaCO3 + Conchiolin)

Quartz Geode/Druzy Quartz

Quartz (SiO₂)

Quartz

Quartz (SiO2 - Silicon Dioxide)

Sandstone

Sandstone (lithified sand)

Pyrite

Iron Pyrite (FeS₂)

Pearl

Aragonite and Conchiolin (CaCO3 + organic protein)

Pearl

Calcium Carbonate (Aragonite/Calcite mixed with Conchiolin), CaCO3

Pink Opal

Hydrated Amorphous Silica (SiO2·nH2O)

Quartz (variety of colors)

SiO2 (Silicon Dioxide)

Aquamarine and clear quartz

Aquamarine (Be3Al2Si6O18), Quartz (SiO2)

Clear Quartz (or Rock Crystal)

Quartz (SiO₂ - Silicon Dioxide)

Pearl

Aragonite / Calcium Carbonate (CaCO3)

Pebble (likely Quartz or Chert)

SiO₂ (Silicon Dioxide) - referring to the likely main mineral composition, Quartz. If it's chert, the scientific name remains SiO₂ with a microcrystalline structure.

Black Pearl (Tahitian Type)

Aragonite / Conchiolin composite (CaCO3)

Amber

Succinite (fossilized resin); C10H16O