Man Made Material, Not A Natural Rock Or Mineral Specimen

Quartz (likely Herkimer Diamond style)

Silicon Dioxide (SiO2)

Tumbled dark stone, likely basalt or chert

Basalt (fine-grained mafic rock), possibly weathered chert; exact identification requires testing

Milky quartz–rich rock

Quartz (SiO₂), likely massive milky quartz with minor dark inclusions

Chert (Flint)

Microcrystalline Quartz (SiO2)

Sandstone

Sedimentary Rock (Quartz arenite)

Pearl (Biogenic Mineraloid)

Calcium carbonate (CaCO3) primarily as Aragonite

Rough amethyst-bearing quartz specimens

Quartz, SiO₂; purple coloration from trace iron and irradiation

Sandstone (likely Quartzose)

Arenite (primarily SiO2)

Rough Citrine Quartz

Silicon Dioxide (SiO2) with iron impurities

Sandstone

Arenite (composed primarily of SiO2)

Sandstone

Arenite (SiO2 based with mineral cements)

Basalt (Greenstone/Water-worn Pebble)

Basalt (containing Chlorite/Epidote)

Sandstone

Arenite (Siliclastic sedimentary rock, primarily SiO2)

Sandstone

Sandstone (Arenite)

Chevron Amethyst

Silicon Dioxide (SiO2) with iron impurities

Iron-stained Quartzite

Metamorphic Quartz (SiO2) with limonite/hematite staining

Sandstone (with Lichen)

Arenite (composed primarily of SiO2)

Tumbled blue stone with a drilled hole

Likely dyed or naturally blue chalcedony/agate; identity cannot be confirmed from the photo

Coquina

Bioclastic Limestone (composed primarily of CaCO3)

Quartz Vein in Siltstone

SiO2 (Quartz) on clastic sedimentary matrix

Generic Rock / Pebble

Undetermined rock specimen

Amethyst

Silicon Dioxide with iron impurities (SiO2)

Sandstone (Limonitic/Iron-stained)

Sandstone (containing Quartz, SiO2, and Limonite, FeO(OH)·nH2O)

Chert Nodule

Microcrystalline Quartz (SiO2)

Blue Onyx (Dyed Agate/Chalky Chalcedony)

Silicon Dioxide (SiO2) with artificial pigment

Chert (Chert / Flint)

Microcrystalline Quartz (SiO2)

Pink Dyed Agate (Pink Agate Slice)

Silicon Dioxide (SiO2) - Chalcedony / Cryptocrystalline Quartz

Yellow Quartz Pebble

Silicon Dioxide (SiO2)

Limestone (specifically Travertine or Tufa)

Calcium Carbonate (CaCO3)

Jasper / Chert (Red)

Cryptocrystalline quartz (SiO2)

Sandstone (likely Arkosic or Quartzose)

Sandstone (SiO2 dominated)

Red Sandstone (Iron-rich)

Arenite (with Hematite cement)

Tumbled black-and-white stone, likely dendritic agate or jasper

Cryptocrystalline quartz (SiO₂), possibly chalcedony with manganese-oxide dendrites

Pink-and-white quartz-rich rock, likely rose quartz matrix

Quartz (SiO₂), possibly intergrown with feldspar or chalcedony

Red Sandstone

Arenite (Iron-rich Sandstone)

Diamond (Cut Specimen)

Diamond (pure carbon, C)

Blue Lace Agate (with Amethyst Geode center)

Silicon Dioxide (SiO2) - Cryptocrystalline Chalcedony

Sandstone

Arenite (primarily SiO2)

Rough Corundum (likely Sapphire/Zircon-bearing)

Aluminium Oxide (Al2O3)

Sandstone

Arenite (predominantly Quartz Sandstone)

Amethyst (Tumbled)

Quartz (Silicon Dioxide, SiO2) with iron impurities

Shale (with Iron Staining)

Argillaceous mudstone / Shale