Likely amphibolite
Amphibolite, composed mainly of hornblende and plagioclase feldspar
metamorphic
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Granite
Coarse-grained felsic intrusive igneous rock, chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende
igneous
Granite (likely weathered granite or granitic gneiss)
Granite; chiefly quartz (SiO₂), feldspar, and mica
igneous
Spinosaurus fossil (permineralized bone)
Spinosaurus aegyptiacus (Calcium phosphate mineralized with silica/sediment)
sedimentary
Vesicular Basalt
Amygdaloidal Basalt (Mafic extrusive volcanic rock)
Igneous
Gneiss
Gneiss
metamorphic
Limonite
FeO(OH)·nH2O
mineral
Peacock Ore
Bornite (Cu5FeS4) or iridescent Chalcopyrite (CuFeS2)
mineral
Quartz (Water-worn pebble)
Silicon Dioxide (SiO2)
mineral
Limonite
FeO(OH)·nH2O
mineral
Dark speckled granite pebble
Granite, a quartz–feldspar–mica plutonic rock
igneous
Weathered basalt pebble
Basalt, a fine-grained mafic volcanic rock; likely containing plagioclase and pyroxene with weathering products
igneous
Granite
Intrusive Phaneritic Felsic Igneous Rock
igneous
Green Fluorite
Fluorite (Calcium Fluoride, CaF2)
mineral
Quartz-rich pegmatite with mica
Granitic pegmatite; mainly quartz (SiO₂), feldspar, and muscovite/biotite mica, with possible sulfide or iron-oxide staining
igneous
Diorite
Diorite (Phaneritic intermediate plutonic rock)
igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
igneous
Gneiss
Gneiss (Metamorphic Rock)
metamorphic
Gneiss (Metamorphic Pebble)
Gneiss (SiO2-rich metamorphic rock)
metamorphic
Gneiss
Gneiss
metamorphic
Granite
Granite (Felsic Plutonic Rock)
igneous
Granodiorite
Granodiorite
igneous
Proustite
Proustite (Ag3AsS3)
mineral
Rough Diamond (Bort)
Diamond (C)
mineral
Amethyst
Silicon Dioxide (Quartz variety)
gemstone
Chevron Amethyst
Silicon Dioxide with Iron Impurities (SiO2)
mineral
Smoky Quartz (Herkimer-style)
Silicon Dioxide (SiO2)
mineral
Limonite/Goethite (Iron Ore)
Hydrous ferric oxides (FeO(OH)·nH2O)
mineral
Limonite (Iron Ore)
FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide mixture)
mineral
Iron Ore (Limonite and Hematite)
Goethite/Limonite (FeO(OH)·nH2O) and Hematite (Fe2O3)
mineral
Pegmatitic granite specimen
Granitic pegmatite, chiefly quartz (SiO₂), feldspar, and mica
igneous
Hag Stone
Perforated sedimentary rock (typically sandstone or limestone)
sedimentary
Granite
Intrusive igneous rock
igneous
Fossil / Permineralized Bone
Tyrannosaurus rex fossil (Hydroxylapatite replaced by various minerals)
sedimentary
Granite
Phaneritic Felsic Igneous Rock
igneous
Granitic Pegmatite with Schorl Tourmaline
Granitic Pegmatite (Schorl: NaFe3Al6(BO3)3Si6O18(OH)4)
igneous
Silver Nuggets (Natural or Cast)
Native Silver (Ag)
mineral
Quartz Geode
Silicon Dioxide (SiO2) in Geodic Cavity
sedimentary
Pyrite (Fool's Gold)
Iron Sulfide (FeS2)
mineral
Cobaltian Calcite
Cobalt-bearing Calcite (Ca,Co)CO3
mineral
Polished serpentine pebble
Serpentinite, chiefly serpentine-group minerals (chrysotile, lizardite, antigorite)
metamorphic
Serpentinite
Serpentinite, composed mainly of serpentine-group minerals (approximately Mg₃Si₂O₅(OH)₄)
metamorphic