Mineral (Chalcedony Variety)

Chert (often called Flint when dark or found in chalk)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (or Flint)

Silicon dioxide (SiO2)

Druzy Quartz

Quartz (Silicon Dioxide, SiO2)

Labradorite

Labradorite ((Ca, Na)(Al, Si)4O8)

Pyrite

Pyrite (Iron Disulfide), FeS2

Rhodonite

Rhodonite (MnSiO3)

Quartzite

Quartzite (SiO2)

Obsidian

Obsidian (principally SiO2)

Chert (White-Tan variety)

Silicon dioxide (SiO2) / Microcrystalline Quartz

Chert (variant of Flint)

Chert (SiO2)

Rutilated Quartz

SiO2 with TiO2 inclusions

Conglomerate (Puddingstone)

Conglomerate (specifically, clastic sedimentary rock)

Gneiss

Gneiss (a metamorphic rock)

Obsidian

Volcanic Glass (comprised primarily of SiO2)

Schist (specifically Chlorite/Greenschist)

Chlorite Schist

Rough Quartz (likely Rose or Amethyst variety)

Silicon Dioxide (SiO2)

Quartz Crystal (specifically a Double-Terminated variety)

Silicon Dioxide (SiO2) - Low Quartz

Basalt (Vesicular)

Extrusive mafic igneous rock; primarily (Mg, Fe)2SiO4 (Olivine), CaAl2Si2O8 (Plagioclase Feldspar), and Pyroxene

Kyanite (Green and Blue varieties)

Kyanite (Al2SiO5)

Obsidian

Volcanic Glass (Amorphous Silica)

Petrified Wood

Silicified Wood (SiO2)

Shale

Shale (clastic sedimentary rock)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Granite (Light-colored quartz/feldspar variety)

Granite (composed primarily of Quartz SiO2 and Feldspar KAlSi3O8)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Diorite (possibly fine-grained variety or a related intermediate intrusive rock like a felsic gabbro or a dark granodiorite)

Diorite (Igneous rock, intrusive, intermediate composition)

Obsidian

Obsidian (Volcanic Glass, primarily SiO2)

Granite

Granite (a broadly defined plutonic igneous rock, often more specifically classified as quartz monzonite or granodiorite based on precise mineral percentages)

Chert (varieties include Flint and Jasper)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Obsidian

Volcanic Glass (Primary composition: SiO2 - Silicon Dioxide)

Sandstone (likely Graywacke or Lithic Sandstone)

Arenite / Wacke (SiO2 based with lithic fragments)

Chert (often referred to as 'Jasper' when red)

Chert (microcrystalline quartz, SiO₂)

Obsidian

Obsidian (Amorphous volcanic glass, SiO2 rich)

Sandstone

Quartz Sandstone (predominantly)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

Chert (Jasper variety) with Iron Oxide staining

Cryptocrystalline Quartz (SiO2) with Goethite/Limonite impurities

Garnet (likely Almandine or a blend)

Garnet group: X3Y2(SiO4)3, where X can be Ca, Mg, Fe2+, Mn2+ and Y can be Al, Fe3+, Cr3+. Given the dark, somewhat reddish-brown appearance in the image, it's likely Almandine (Fe3Al2(SiO4)3) or a mix with other iron-rich garnets.

Chlorastrolite (Greenstone)

Chlorastrolite (Pumpellyite variety), Ca2(Mg,Fe)Al2(SiO4)(Si2O7)(OH)2·H2O

Buffalo Nickel (Indian Head Nickel)

Cupronickel (75% Copper, 25% Nickel)

Quartzite

Quartzite (Primary mineral: Silicon Dioxide, SiO2)

Emerald

Beryl (Be₃Al₂Si₆O₁₈), specifically the green variety colored by trace amounts of chromium or vanadium.