Mineral, Possibly Rock Fragment Containing A Mineral

Granitic Pegmatite

Pegmatitic Granite

Sandstone (Ferruginous)

Arenite with Iron Oxide cement

Fossiliferous Limestone

Biogenic Limestone (CaCO3)

Basalt with Peridotite Xenolith

Mafic Igneous Rock with Peridotite Inclusion (Olivine-rich)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Yellow Quartz

Silicon Dioxide (SiO2)

Weathered Volcanic Rock (possibly Rhyolite or Andesite Pebble)

Volcanic rock (e.g., Rhyolite or Andesite, specific identification would require thin section analysis or chemical assay). Mineral composition: Primarily feldspars (orthoclase and/or plagioclase), quartz (in rhyolite), micas, amphiboles, and sometimes pyroxenes.

Flower Agate

Silicon Dioxide (SiO2) with Plume Inclusions

Schist

Mica Schist (Medium-grade Metamorphic Rock)

Fuchsite in Quartz

Chromium-rich Muscovite (K(Al,Cr)2(AlSi3O10)(OH)2) in Quartz (SiO2)

Basalt

Extrusive igneous rock

Tumbled blue sodalite (probable)

Sodalite, Na₈(Al₆Si₆O₂₄)Cl₂; possibly lapis-lazuli if lazurite is present

Quartz in Matrix (possibly Basalt or Siltstone host)

Silicon Dioxide (SiO2) in Host Rock

Conglomerate

Conglomerate (clastic sedimentary rock)

Amygdaloidal Basalt

Amygdaloidal Basalt containing Zeolite or Quartz (SiO2/Silicates)

Fossil shell fragment, likely brachiopod or bivalve

Indeterminate fossilized carbonate shell; possibly Spiriferida (brachiopod)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Pegmatite

Pegmatite (felsic intrusive igneous rock)

Dark river-worn cobble, possibly basalt or fine-grained volcanic rock

Likely basaltic rock; exact identification requires a fresh surface and tests

Quartz (Druzy or Geode fragment)

Silicon Dioxide (SiO2)

Sandstone (Quartzite-rich)

Clastic Sedimentary Rock (primarily SiO2)

Amethyst

SiO2 (Silicon Dioxide with Iron impurities)

Quartz Heart or Arrowhead Shape

Silicon Dioxide (SiO2)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with iron oxide staining/cementing)

Quartz vein in Schist

Crystalline Silicon Dioxide (SiO2) in Metamorphic Host

Quartz

Silicon Dioxide (SiO2)

Geode (Unopened)

Siliceous Geode (SiO2)

Geode Nodules / Keokuk Geode

Quartz / Chalcedony Geode (SiO2)

Calcite-rich limestone fragment

Limestone, predominantly calcite (CaCO₃), possibly micritic or fossiliferous

Quartz (likely) or a Quartzite Pebble

Silicon dioxide (SiO2) for quartz. If it's quartzite, it's a metamorphic rock primarily composed of quartz.

Sandstone (likely Quartzose Sandstone with mineral staining)

Arenite (composed mainly of SiO2)

Green Aventurine

Silicon Dioxide (SiO2) with inclusions of Fuchsite mica

Concretion

Sedimentary Concretion (Ironstone / Calcite Concretion)

Pegmatite

Granitic Pegmatite

Generic Pebble / Small Rock Fragment

Lithic fragment / Weathered rock particle

Dendritic Agate

Dendritic Agate (Silicon Dioxide with Manganese or Iron Oxide inclusions, SiO2)

Shale

Fissile Mudstone (Shale)

Fossiliferous Limestone

Fossiliferous Calclutite / Bio-calcarenite (CaCO3)

Sandstone with Iron Banding

Arenite with Hematite or Limonite staining (SiO2 with Fe2O3)

Conglomerate

Conglomerate (Clastic Sedimentary Rock)

Chert or flint fragment

Microcrystalline quartz (SiO₂), commonly chalcedony with possible clay/iron-oxide impurities

Shale

Lutaceous sedimentary rock