Sedimentary Or Igneous Fragment

Chert (Arrowhead Preform)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Ironstone Concretion

Siderite or Goethite Concretion

Gneiss

Gneiss (High-grade Regional Metamorphism)

Quartz–mica metamorphic rock, likely schist

Quartz–muscovite/biotite schist; predominantly SiO₂ quartz with phyllosilicate micas

Quartzite with Mica / Gneiss Pebble

Metamorphic Rock (Quartz-Feldspar-Mica aggregate)

Weathered sandstone fragment

Quartz-rich sandstone, likely ferruginous sandstone

Amethyst Geode Fragment

Quartz (SiO2) with trace iron impurities

Weathered dark rock fragment

Indeterminate; possibly basalt or iron-rich volcanic rock

Weathered granite or granitic gneiss fragment

Granite; chiefly quartz, alkali feldspar, plagioclase, and minor mica/iron oxides

Oolite (Ooid)

Oolitic Limestone (chiefly CaCO3)

Quartz in Matrix (possibly with Biotite or Hornblende)

Quartz (Silicon Dioxide, SiO2) in Granitic Matrix

Coquina with Calcite Crystals

Calcareous Bioclastic Grainstone (CaCO3)

Sandstone (Ferruginous)

Arenite with Iron Oxide cement (SiO2 + Fe2O3)

Quartz (Iron-stained or Chalcedony varieties)

Silicon Dioxide (SiO2)

Uncertain small pale mineral fragment

Indeterminate; possibly calcite or a light-colored feldspar fragment

Ironstone Concretion

Siderite or Hematite Concretion

Chert (and Chert Flake)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

River Pebble (Granitic Sandstone)

Clastic sedimentary rock (Lithic Arenite)

Chalcedony Geode Fragment

Cryptocrystalline Quartz (SiO2)

Chalcedony (Agate/Seashell replacement)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Tiny amber-colored crystal fragment

Indeterminate; possibly quartz, feldspar, mica, or a sulfide mineral

Quartz

Silicon Dioxide (SiO2)

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Lichen-covered graywacke or granitic glacial cobble

Indeterminate; likely quartz–feldspar–mica rock, possibly weathered granite or granodiorite

Weathered granite-like rock

Granite, likely biotite-bearing; exact identification is uncertain from the image

Rounded weathered rock, likely basalt or andesite

Fine-grained mafic to intermediate volcanic rock; precise identification requires testing

Granite

Phaneritic plutonic rock (composed of Quartz, Alkali Feldspar, and Plagioclase)

Basalt pebble

Basalt

Quartz (Clear Quartz)

Silicon Dioxide (SiO2)

Jasper

Jasper (Silicon Dioxide, SiO2 plus iron oxide impurities)

Quartz (Milk or Clear Variety)

Silicon Dioxide (SiO2)

Quartz (Vein Quartz)

Silicon Dioxide (SiO2)

Polished petrified wood

Silicified wood, primarily microcrystalline quartz (SiO₂) replacing organic tissue

Smoky quartz fragment

Quartz, silicon dioxide (SiO₂), smoky variety

Milky Quartz (Druzy Geode fragment)

Silicon Dioxide (SiO2)

Chalcedony Geode Fragment

Microcrystalline Quartz (SiO2) within a nodule

Quartz on Matrix

Silicon Dioxide (SiO2)

Weathered granite or granodiorite fragment

Granite–granodiorite, chiefly quartz, feldspar, and dark biotite/amphibole

Banded Agate (Geode Fragment)

Silicon Dioxide (SiO2) - Variety Agate

Quartz

Silicon Dioxide (SiO2)

Red Sandstone or Brick Fragment

Arenite (if sandstone)

Gneiss (Green Gneiss)

Gneiss (High-grade Regional Metamorphic Rock)