Sedimentary (Secondary Classification For A Weathered Mineral Specimen)

Ferruginous Quartz (River Pebble)

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Sandstone Cobble

Arenite (Secondary classification based on grain size)

Granite or granitic rock fragment

Felsic intrusive igneous rock, typically quartz + feldspar + mica; exact species uncertain from the image

Bituminous Coal (with Anthracite or Vitrinite inclusion)

Organic-rich Sedimentary Rock (Carboniferous classification)

Green Quartz (Prasiolite/Adventurine)

Silicon Dioxide with inclusions (SiO2)

Limonite

FeO(OH)•nH2O

Granite (likely biotite granite)

Coarse-grained granitic rock; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende

Limonite / Ironstone

FeO(OH)·nH2O

Dark metamorphic rock, likely hornfels or fine-grained basalt

Probable hornfels; commonly quartz–feldspar–mica with variable amphibole/pyroxene

Quartz (Small Pebble)

Silicon Dioxide (SiO2)

Sandstone

Arenite (Secondary classification based on grain size)

Weathered quartz-bearing rock, possibly granite or gneiss

Indeterminate; likely quartz–feldspar–mica aggregate, possibly granitic gneiss

Mixed Rock and Mineral Collection

Various geological specimens

Limonite (Ironstone)

Goethite/Limonite (Hydrated iron(III) oxide-hydroxide)

Quartz-rich rock, likely milky quartz vein material

Quartz (SiO₂), possibly quartzite or quartz-bearing pegmatite

Quartz-rich rock fragment, possibly chert or weathered quartz

Microcrystalline quartz (SiO₂), tentative identification

Yellow Quartz (Chert/Chalcedony)

Silicon Dioxide (SiO2) with iron inclusions

Polished pink granite cobble

Granite, chiefly potassium feldspar, plagioclase, quartz, and biotite/hornblende

Limonite / Ironstone Nodule

Hydrated Iron Oxide (FeO(OH)·nH2O)

Yellow Quartz

Silicon Dioxide (SiO2)

Dendritic sandstone

Sandstone with Manganese Oxide dendrites

Iron-rich meteorite candidate

Unclassified stony-iron or iron meteorite candidate; possibly limonite/hematite-bearing terrestrial rock

Rounded river cobble, likely weathered sandstone or quartz-rich metasandstone

Indeterminate sandstone; commonly quartz (SiO₂) with feldspar, lithic grains, and iron-oxide cement

Likely iron-stained quartz or feldspar fragment

Quartz (SiO₂) or potassium feldspar (KAlSi₃O₈), uncertain from image

Agate (Chert/Chalcedony)

Silicon Dioxide (SiO2)

Chert on Volcanic Host Rock

Sedimentary Chert (SiO2) within Basalt or Andesite

Quartz Pebble (likely Chalcedony or Quartzite)

Silicon Dioxide (SiO2)

Botryoidal Hematite (included in Quartz/Limonite matrix)

Fe2O3 (Hematite) on Quartz (SiO2) / Limonite

Limonite (Iron Ore)

Hydrated ferric oxide (FeO(OH)·nH2O)

Limonite (often after Hematite or Goethite)

Limonite (FeO(OH)·nH2O)

Amygdaloidal Basalt

Extrusive mafic igneous rock with amygdules

Limonite Concretion

FeO(OH)qnH2O (Hydrated iron(III) oxide-hydroxide mixture)

Rounded gray river pebble, likely basalt or andesite

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

Red jasper pebble

Microcrystalline quartz (chalcedony), SiO₂, colored by iron oxides

Small pale rock fragment

Indeterminate; possibly quartz, calcite, or a weathered feldspar-rich fragment

Copper Ore (Malachite and Limonite bearing rock)

Copper-bearing rock with secondary copper minerals

Conglomeratic breccia

Clast-supported polymictic conglomerate/breccia, cemented by silica- or carbonate-rich matrix

Erythrite

Erythrite (Cobalt Bloom) - Co3(AsO4)2·8H2O

Quartz Geode

Silicon Dioxide (SiO2)

Unidentified Rock Fragment

Unknown

Jasper Agate

Chalcedony (Silicon Dioxide - SiO2)

Possible iron-rich meteorite

Uncertain; likely an ordinary chondrite (stony meteorite), pending testing