Sedimentary (Secondary Classification For A Weathered Mineral Specimen)

Ferruginous Quartz (River Pebble)

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Coarse-grained metamorphic rock, likely gneiss

Biotite–quartz–feldspar gneiss (probable; exact identification requires a fresh surface and tests)

Small weathered mineral/rock fragment

Indeterminate; possibly quartz-bearing feldspathic rock or calcite-rich specimen

Iron-rich breccia or weathered limonite-bearing rock

Goethite–limonite ironstone, possibly ferruginous breccia

Sandstone Cobble

Arenite (Secondary classification based on grain size)

Weathered gray-green basaltic rock

Basalt, likely altered to low-grade greenschist/amphibolite facies

Weathered iron-rich rock, possibly banded iron formation

Hematite–goethite-rich ironstone; possible BIF (Fe₂O₃/FeO(OH) with quartz)

Quartz-bearing dark rock, possibly hornfels or basalt

Probable quartz–feldspar rock; exact identification requires testing

Weathered quartz-rich rock, possibly quartzite or granite fragment

Quartzite (SiO₂-dominant) or altered granitoid; uncertain from image

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, potentially granitic, or recrystallized quartzite

Sandstone

Arenite (Secondary classification based on grain size)

Banded gneiss

Gneiss, typically quartz–feldspar–mica ± amphibole

Bituminous Coal (with Anthracite or Vitrinite inclusion)

Organic-rich Sedimentary Rock (Carboniferous classification)

Granite or granitic rock fragment

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

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz (SiO₂) with feldspar and minor dark minerals

Weathered quartz-rich rock, possibly chert or quartzite

Likely microcrystalline quartz (SiO₂), but exact identification is uncertain from the photograph

Green Quartz (Prasiolite/Adventurine)

Silicon Dioxide with inclusions (SiO2)

Limonite

FeO(OH)•nH2O

Granite (likely weathered granite or granitic gneiss)

Granite; primarily quartz (SiO₂), feldspar, and mica (biotite/muscovite)

Granite (likely biotite granite)

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

Weathered quartz-rich rock, possibly milky quartz or quartzite

Quartz (SiO₂); likely quartzite if the granular texture is recrystallized sandstone

Small quartz-rich rock fragment

Likely quartz-bearing feldspathic rock; exact identification is limited by the image

Weathered quartz-rich rock, likely arkose or quartzite

Quartz-dominant siliciclastic rock; probable arkose (quartz + feldspar), possibly weakly metamorphosed quartzite

Quartz (Small Pebble)

Silicon Dioxide (SiO2)

Limonite / Ironstone

FeO(OH)·nH2O

Weathered granite or granitic gneiss

Quartz–feldspar–mica granitoid; possible biotite granite or gneiss

Likely iron-rich meteorite fragment

Unclassified iron oxide–rich meteorite; composition cannot be confirmed visually

Possible basaltic volcanic rock or iron-rich meteorite

Likely basalt (plagioclase–pyroxene rock); meteorite status cannot be confirmed visually

Weathered sandstone or quartzite cobble

Quartz-rich sandstone; possibly weakly metamorphosed quartzite

Dark metamorphic rock, likely hornfels or fine-grained basalt

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

Weathered brown-gray igneous rock, likely basaltic andesite

Porphyritic basaltic andesite; probable plagioclase–pyroxene volcanic rock

Mixed Rock and Mineral Collection

Various geological specimens

Limonite (Ironstone)

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

Quartz-rich rock fragment, possibly chert or weathered quartz

Microcrystalline quartz (SiO₂), tentative identification

Road-surface aggregate (crushed stone)

Unidentifiable mixed lithic aggregate; likely basaltic/andesitic fragments with feldspar, quartz, and weathered rock

Yellow Quartz (Chert/Chalcedony)

Silicon Dioxide (SiO2) with iron inclusions

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz (SiO₂) with feldspar and minor mica, or quartzite

Quartz-rich feldspathic rock, possibly weathered granite or quartzite

Likely quartz and feldspar aggregate; exact identification is uncertain from the photograph

Limonite / Ironstone Nodule

Hydrated Iron Oxide (FeO(OH)·nH2O)

Weathered quartz-bearing rock, possibly granite or gneiss

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

Yellow Quartz

Silicon Dioxide (SiO2)

Dendritic sandstone

Sandstone with Manganese Oxide dendrites