Metamorphic (Altered Igneous Rock)

Rounded dark pebble, possibly weathered basalt

Fine-grained mafic volcanic rock; likely basalt, but identification is uncertain from the photograph

Epidote

Epidote; Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

Quartz-rich granite or granitic gneiss

Granite; chiefly quartz (SiO₂), feldspar, and mica, possibly weakly metamorphosed

Purple Dyed Dalmatian Stone

Dyed Peralkaline Trachyte

Wollastonite

Calcium Inosilicate, CaSiO3

Unidentified rounded rock, likely granite or granitic gneiss

Quartz–feldspar–mica rock; exact identification is uncertain from the image

Epidosite

Epidosite (consisting primarily of Epidote Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH) and Quartz SiO2)

Gabbro (likely olivine-bearing)

Coarse-grained mafic intrusive rock; chiefly plagioclase feldspar and pyroxene, possibly olivine

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) in Altered Host Rock

Green aventurine (tumbled)

Quartz-rich aventurine; predominantly microcrystalline SiO₂ with fuchsite mica inclusions

Weathered granitic rock

Granite or granodiorite; primarily quartz (SiO₂), feldspar, and mica

Weathered quartz-rich pebble, possibly quartzite or granite fragment

Quartzite (mostly SiO₂), though the specimen may contain feldspar and other silicates

Tumbled greenish jasper

Jasper, microcrystalline quartz (SiO₂) with iron-bearing and clay-mineral impurities

Peridotite (Dunite/Lherzolite)

Ultramafic Peridotite

Red jasper in a gray host rock (likely jasperized volcanic rock)

Microcrystalline quartz (SiO₂), iron-oxide–colored jasper, in a fine-grained volcanic or sedimentary matrix

Tumbled tiger’s-eye-rich quartzite

Quartzite, composed mainly of microcrystalline quartz (SiO₂) with fibrous crocidolite pseudomorphs and iron oxides

Unakite-like polished pebble

Epidote–K-feldspar–quartz rock (likely altered granite; identification from image is provisional)

Unakite

Altered granite (Epidote, Orthoclase Feldspar, and Quartz)

Green Granite / Verd Antique

Serpentinite / Metasomatized Peridotite

Serpentinite

Serpentinite, a rock composed mainly of serpentine-group minerals (approximately Mg₃Si₂O₅(OH)₄)

Quartz-veined dark metamorphic rock, likely marble or serpentinite

Calcite- or magnesite-veined serpentinite/marble; exact identification requires testing

Likely mica-rich schist

Mica schist, probably muscovite/biotite-bearing quartz schist

Serpentinite (likely)

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly after peridotite

Iron-rich breccia or weathered ironstone

Goethite–hematite-bearing limonite, possibly with quartz and altered rock fragments

Polished granite pebble

Granite; chiefly quartz, feldspar, and mica/amphibole

Serpentinite with green serpentine inclusion

Serpentinite; serpentine-group minerals, chiefly antigorite, lizardite, or chrysotile, with possible magnetite

Weathered porphyritic volcanic rock

Likely altered andesite or rhyolite porphyry

Granite (weathered fragment)

Granite; chiefly quartz, alkali feldspar, plagioclase, and mica

Citrine

Silicon Dioxide (SiO₂)

Citrine

Silicon Dioxide (SiO2)

Tumbled blue-gray stone, likely basalt or slate

Probable fine-grained basalt; exact identification is uncertain from the photograph

Greenstone / altered basalt fragment

Likely chlorite–epidote–actinolite altered basalt; exact identification requires testing

Weathered rhyolite or volcanic tuff

Silica-rich extrusive igneous rock, likely rhyolite; exact identification requires testing

Green-brown metamorphic rock, possibly serpentinite

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite, chlorite, or carbonate

Veined basalt or dark mafic metamorphic rock

Basalt, likely altered and quartz/calcite-veined; exact identification requires testing

Weathered granite or granitic gneiss

Quartz–feldspar–mica rock; likely granitoid, possibly weakly gneissic

Pyrite-bearing rock (likely pyrite-rich schist or quartzite)

Pyrite, FeS₂, disseminated in a metamorphic host rock

Weathered brown-gray igneous rock, likely basaltic andesite

Porphyritic basaltic andesite; probable plagioclase–pyroxene volcanic rock

Serpentine-rich altered rock

Serpentinite, likely with chlorite and magnetite; exact identification requires testing

Likely serpentinite (serpentine-rich rock)

Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, olivine, and pyroxene

Polished rhyolite (likely porphyritic rhyolite)

Rhyolite, composed chiefly of quartz and alkali feldspar with minor plagioclase, biotite, and iron oxides

Polished brown river pebble

Likely quartzite or weathered metabasalt; exact identification requires hardness and streak tests