Magnetite
Magnetite (Fe3O4)
mineral
Category
Synthetic Or Natural Fiber
Browse synthetic or natural fiber specimens identified by the Rock Identifier community.
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Sandstone (Ferruginous)
Ferruginous Sandstone (SiO2 with Fe2O3)
sedimentary
Sandstone (with Possible Iron Staining/Crust)
Arenite (SiO2 based)
sedimentary
Obsidian
Vitreous volcanic silicate (70-75% SiO2)
igneous
Shale
Shale (clastic sedimentary rock composed of silt and clay-sized particles)
sedimentary
Mohave Turquoise (Composite/Stabilized)
Hydrated copper aluminium phosphate (CuAl6(PO4)4(OH)8·4H2O) with stabilizing resin and metallic inclusions
mineral
Sandstone (Quartzose Sandstone)
Arenite (primarily SiO2)
sedimentary
Sandstone (with Iron Staining)
Clastic sedimentary rock (primarily Quartz - SiO2)
sedimentary
Sandstone
Arenite (SiO2 primarily)
sedimentary
Smoky Quartz
Silicon Dioxide (SiO2) with trace aluminum and irradiation
mineral
Corundum (Ruby variety)
Aluminium oxide (Al2O3)
mineral
Diamond
Native Carbon (C)
mineral
Dyed Agate (Tumbled)
Silicon Dioxide (SiO2) - stained microcrystalline quartz
sedimentary
Gold Nugget
Native Gold (Au)
Mineral
Agate
SiO2
Mineral
Agate Geode
Microcrystalline Quartz (SiO2)
mineral
Black Onyx
Cryptocrystalline Quartz (SiO2)
mineral
Coarse Sand and River Gravel
Siliciclastic Sediment (primarily Quartz and Feldspar)
sedimentary
Sandstone (Ferruginous)
Arenite with Iron-Oxide Cement
sedimentary
Almandine Garnet & Tumbled Citrine Quartz
Fe3Al2(SiO4)3 (Garnet) and SiO2 (Quartz)
mineral
Diamond (Set in Jewelry)
C (Native Carbon)
mineral
Blue Sapphire
Corundum (Al2O3)
mineral
Hag Stone
Sandstone or Limestone with Solution Holes (Bioturbation/Erosion)
sedimentary
Granite
Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8, CaAl2Si2O8)
igneous
Granite (River-worn pebble)
Phaneritic plutonic rock (SiO2 + Al2O3)
igneous
Diamond
Diamond (pure native carbon, C)
mineral
Diamond (Colorless/White)
Carbon (C)
mineral
Dyed Agate
Silicon Dioxide (SiO2) - Variety Agate / Chalcedony
mineral
Basalt
Basalt (Mafic volcanic rock)
igneous
Veined Limestone (Micrite) with Quartz/Calcite Veins
Calcium Carbonate (CaCO3) with Silicate or Carbonate inclusions
sedimentary
Conglomerate
Conglomerate (Clastic sedimentary rock)
sedimentary
Cullet Glass (sometimes mistaken for Blue Obsidian or Slag)
Amorphous Silicon Dioxide (SiO2) with chemical additives (e.g., Cobalt for blue color)
mineraloid / industrial byproduct
Turquoise (Blue Howlite / Magnesite imitation)
CuAl6(PO4)4(OH)8·4H2O (for natural Turquoise); Ca2B5SiO9(OH)5 (for Howlite)
mineral
Smoky Quartz
Silicon Dioxide (SiO2)
mineral
Magnetite / Iron-Rich Concretion
Magnetite (Fe3O4) or Bog Iron Limonite
mineral
Limestone (specifically Travertine or Tufa)
Calcium Carbonate (CaCO3)
sedimentary
Rough Diamond
Diamond (pure Carbon, C)
mineral
Sandstone (likely Arkosic or Lithic)
Clastic Sedimentary Rock (SiO2 with accessory minerals)
sedimentary
Diamond
C (Carbon)
mineral
Diamond (in jewelry setting)
Cubic Carbon (C)
mineral
Hag Stone
Naturally holed stone (typically sedimentary rock such as flint, limestone, or sandstone)
Sedimentary
Vesicular Basalt
Extrusive mafic igneous rock
igneous