Metamorphic (Altered Igneous Rock)

River Pebble (Granite/Gneiss)

Granitic Pebble (Quartz, Feldspar, Mica composition)

Unidentified greenish-gray rock fragment

Tentatively altered basalt or basaltic volcanic rock; mineral identification requires testing

Blue Apatite

Fluorapatite / Apatite Group (Ca5(PO4)3(F,Cl,OH))

Polished tiger iron

Tiger iron; quartz (SiO₂) with hematite/magnetite and crocidolite-derived riebeckite/goethite

Weathered quartz-bearing metamorphic rock, likely gneiss or schist

Quartz–feldspar–mica rock; exact classification is uncertain from the photograph

Weathered granitic or gneissic pebble

Granite–gneiss assemblage; quartz + feldspar + dark mafic minerals

Quartz with inclusions (likely Chlorite or Hornblende) and country rock

SiO2 (Quartz) with associated ferromagnesian minerals

Polished black stone, likely basalt or amphibolite

Basalt (fine-grained mafic rock), possibly amphibolite; primarily plagioclase and pyroxene/amphibole

Black Tourmaline (Schorl)

NaFe3+3Al6(BO3)3Si6O18(OH)4

Unakite

Unakite (altered granitic rock)

Weathered basalt or mafic metavolcanic rock

Basalt, possibly altered to greenstone (chlorite–epidote–actinolite assemblage)

Fine-grained green-gray rock pebble, likely basalt or greenstone

Probable basalt (plagioclase and pyroxene), possibly altered to greenstone

Epidote

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

Pink-and-green mineral specimen, possibly unakite

Unakite, an epidote–feldspar–quartz rock; identification is uncertain from the photo

Weathered, rounded polymictic pebble (likely volcanic or metamorphic rock)

Indeterminate; possibly altered basalt, greenstone, or epidote-bearing metamorphic rock

Quartz-veined altered rock

Likely quartz-bearing metasediment or altered igneous rock; vein mineral: quartz (SiO₂)

Greenstone / serpentinite-like metamorphic rock

Probable serpentinite-rich greenschist; commonly dominated by serpentine-group minerals, chlorite, actinolite, and magnetite

Unakite

Unakite (altered granite containing Epidote, Orthoclase, and Quartz)

Milky quartz in weathered host rock

Quartz, SiO₂; likely a quartz vein in altered country rock

Possibly biotite-rich mica schist or weathered mafic rock

Mica schist; chiefly biotite mica, quartz, and feldspar

Unakite

Altered Granite (Unakite)

Unakite

Unakite (Altered Granite)

Large rough rock, likely granite or granitic gneiss

Possibly granite; exact identification is uncertain from the photograph

Weathered schist or gneiss boulder

Micaceous quartz-feldspar schist/gneiss; exact identification is limited by the photograph

Lapis Lazuli

Na8(Al6Si6O24)S2 (Lazurite is the primary constituent mineral)

Greenstone pebble (likely altered basalt or serpentine)

Greenschist-facies mafic rock; commonly chlorite–actinolite–epidote ± serpentine

Lapis Lazuli

Lapis lazuli (complex rock primarily composed of Lazurite (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2 with Calcite and Pyrite)

Likely serpentinite (serpentine-rich rock)

Serpentinite, composed mainly of serpentine-group minerals (e.g., antigorite, lizardite, or chrysotile)

Weathered granitic or metamorphic rock fragment

Indeterminate; likely quartz–feldspar–mica-bearing granitoid or gneiss

Milky quartz vein in altered host rock

Quartz (SiO₂), likely with feldspar, mica, and iron-oxide alteration

Banded River Cobble with Mafic Dike

Hydrothermally altered Graywacke or Sandstone with Mafic Intrusion

Unakite

Unakite (altered granitic rock)

Likely greenstone (metamorphosed mafic rock)

Greenstone; commonly metamorphosed basalt or dolerite, with chlorite, actinolite, epidote, and albite

Quartz Vein in Greenstone

Metamorphic rock with quartz vein (SiO2 / mixed silicates)

Mixed river-worn rock and mineral collection

Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble

Greenstone (likely altered basalt)

Chlorite- and/or epidote-altered mafic volcanic rock; exact identification needs close examination

Granite-like rock

Felsic intrusive igneous rock, probably granitic or granodioritic

Altered volcanic rock, possibly andesite

Likely porphyritic andesite or dacite with secondary chlorite/epidote and quartz–calcite veins

Likely serpentinite (greenstone pebble)

Serpentinite, composed mainly of serpentine-group minerals (e.g., lizardite, chrysotile, or antigorite)

Granite or granitic rock fragment

Coarse-grained felsic intrusive rock, chiefly quartz, feldspar, and mica/amphibole

Likely iron-rich metamorphic rock (possibly hematite-rich ironstone)

Unidentified ferruginous rock; exact mineralogy cannot be determined from the image

Greenstone, likely altered basalt

Metabasalt (chlorite–actinolite–epidote assemblage), likely greenschist-facies greenstone