Biotite mica (likely)
Biotite, a mica-group mineral; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂
mineral
Category
Not A Geological Specimen
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Small rough mineral/rock specimen (not confidently identifiable)
Undetermined; image detail is insufficient for a reliable identification
mineral
Fossilized Gastropod Internal Mold
Gastropoda (Steinkern fossil)
fossil
Quartz pebble
Silicon dioxide (SiO2)
mineral
Polymictic conglomerate
Lithified polymictic conglomerate; clasts likely quartzite, granite, and volcanic rock in a dark matrix
sedimentary
Quartz Vein in Basalt or Slate
Hydrothermal quartz vein traversing mafic host rock
metamorphic
Ironstone Concretion
Ferruginous Concretion / Limonite-Goethite Aggregate
sedimentary
Quartz-rich conglomeratic sandstone
Lithic arkose/conglomerate, dominated by quartz and feldspar grains
sedimentary
Almandine Garnet
Almandine (Fe3Al2Si3O12)
mineral
Vein Quartz in Basalt or Chert
Silica-veined dark lithic rock (Quartz veins in microcrystalline matrix)
sedimentary
Decorative mosaic cross containing mixed rock and glass fragments
Polychrome aggregate; likely quartz, feldspar, marble, granite, and assorted colored glass
mineral
Weathered light-colored rock fragment, possibly quartz-rich rock
Undetermined; appearance may be quartzite or a quartz-rich granite fragment
igneous
Small brown mineral fragment (undetermined)
Unidentified; image detail is insufficient for a reliable species identification
mineral
Possible fossilized ammonite or concretion
Indeterminate fossil specimen; possibly an ammonoid mold/cast in iron-rich sedimentary rock
fossil
Tumbled quartz-rich rock, likely milky quartz with brown iron staining
Quartz (SiO₂), possibly in a weathered quartz-bearing rock; exact host rock cannot be determined from the photo
igneous
Weathered stone nodule or concretion
Unidentified lithic concretion; composition cannot be determined from the image
sedimentary
Quartz
Silicon dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Weathered gray stone fragment
Undetermined; possibly limestone or sandstone
sedimentary
Siltstone Concretion
Carbonate-cemented Siltstone Concretion
sedimentary
Quartz Vein in Host Rock
Silicon dioxide (SiO2) veins in metamorphic/igneous host rock
igneous
Almandine Garnet
Almandine, Fe3Al2(SiO4)3
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Sandstone with Quartz Vein
Arenite with SiO2 intrusion
sedimentary
Likely a small rough mineral specimen
Unidentifiable from the image; possibly a mica-bearing rock or green mineral
mineral
Unidentified dark-gray rock fragment
Undetermined; the photo is insufficient for reliable mineral or rock identification
igneous
Granite with Tourmaline or Biotite
Phaneritic Igneous Rock (Granoid)
igneous
Quartz
Silicon Dioxide (SiO2)
mineral
Milky Quartz
Silicon Dioxide (SiO2)
mineral
Flint in Limestone (Chert Nodule)
Sedimentary rock containing microcrystalline quartz (SiO2) within a carbonate matrix
sedimentary
Quartz Crystal Cluster
Silicon Dioxide (SiO2)
mineral
Small gray rock fragment
Unidentified rock; the image lacks enough detail for reliable mineral identification
igneous
Geode with Quartz and Chalcedony
Silicon Dioxide (SiO2)
sedimentary
Likely biotite mica
Biotite, a dark mica-group mineral; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂
mineral
White Quartz
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Quartz with Iron Oxide
Silicon Dioxide (SiO2)
mineral
Quartz
Silicon Dioxide (SiO2)
mineral
Quartz (Milky or Iron-stained)
Silicon Dioxide (SiO2)
mineral