Metamorphic (Altered Igneous Rock)

Likely tumbled dark volcanic rock

Probably basalt or fine-grained andesite; exact identification requires testing

Rhyolite or jasper-bearing volcanic rock

Rhyolite, likely altered and silicified; red coloration may come from hematite

Weathered basalt pebble

Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase, clinopyroxene, and iron-rich oxides

Likely limestone or marble fragment

Calcite-rich carbonate rock; CaCO₃

Likely granite

Granite, a coarse-grained felsic intrusive igneous rock

Quartz-rich granitic rock, possibly weathered pegmatite

Granite or pegmatitic quartz–feldspar aggregate; mainly SiO₂ quartz with K-feldspar/plagioclase and minor mica

Weathered porphyritic volcanic rock, likely andesite

Porphyritic andesite; primarily plagioclase feldspar, pyroxene, and possibly amphibole in a fine-grained groundmass

Reddish foliated metamorphic rock, likely phyllite

Phyllite, typically quartz–mica–chlorite with iron-oxide staining

Dyed Agate

SiO2

Iron-stained quartz-rich rock, possibly ironstone or quartz-vein material

Quartz (SiO₂) with iron oxides/hydroxides; exact host rock cannot be determined from the image

Dalmatian jasper

Spotted rhyolite (commercially called Dalmatian jasper), chiefly quartz and feldspar with black aegirine/arfvedsonite inclusions

Blue quartz-bearing rock, possibly chrysocolla-bearing quartzite

Quartz (SiO₂), with probable blue chrysocolla or copper-bearing clay minerals; exact identification requires testing

Polished quartz-rich breccia

Quartz–feldspar breccia; predominantly SiO₂ with feldspar and iron-oxide minerals

Tumbled yellow jasper or iron-stained quartzite

Microcrystalline quartz (SiO₂), likely jasper/quartzite with iron-oxide staining

Orbicular jasper / brecciated jasper slab

Silicified volcanic rock composed mainly of microcrystalline quartz (SiO₂), with iron-oxide and possible chalcedony/agate bands

Greenstone / altered basalt (probable)

Chlorite–actinolite–epidote rock; commonly derived from basalt or gabbro

Likely weathered quartz-bearing rock fragment

Indeterminate granitic or quartz-rich silicate rock; chiefly quartz (SiO₂), possibly feldspar

Serpentine-rich metamorphic rock

Serpentinite, likely with magnetite and weathered ultramafic minerals

Weathered basaltic river pebble

Basalt, likely altered or partially vesicular basalt

Weathered rhyolitic tuff or altered volcanic rock

Felsic volcanic tuff, likely devitrified or hydrothermally altered

Serpentinite (serpentine-rich metamorphic rock)

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

Rounded greenish river pebble

Likely altered basalt or greenstone (metabasalt); exact identification requires testing

Weathered volcanic rock, likely altered andesite

Altered andesite; predominantly plagioclase and volcanic pyroxene/amphibole, with secondary iron oxides and clay minerals

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Tumbled pink-orange feldspar

Microcline or orthoclase feldspar, KAlSi₃O₈ (tentative)

Likely epidote-bearing rock or weathered chalcopyrite specimen

Epidote-group mineral, possibly with chalcopyrite; identification uncertain from image

Porphyritic volcanic rock, likely andesite or basaltic andesite

Fine-grained plagioclase–pyroxene volcanic rock; exact identification requires microscopy or chemical testing

Rounded river pebble, likely basaltic or andesitic volcanic rock

Fine-grained mafic to intermediate volcanic rock; likely basalt/andesite, but exact identification requires testing

Tumbled greenstone, likely serpentine or altered jade-like rock

Serpentinite (predominantly serpentine-group minerals; Mg₃Si₂O₅(OH)₄), possibly nephrite jade if notably tough and dense

Tumbled reddish-brown volcanic rock, likely basalt or andesite

Fine-grained mafic to intermediate igneous rock; commonly plagioclase with pyroxene and/or olivine, possibly iron oxides

Polished basalt pebble

Vesicular to amygdaloidal basalt, composed mainly of plagioclase, pyroxene, and iron-rich oxides

Likely weathered sandstone or metasandstone

Quartz-rich sandstone (possibly weakly metamorphosed metasandstone)

Vesicular volcanic rock, likely pumice or weathered scoria

Pumice/scoria; predominantly volcanic glass and plagioclase, with possible pyroxene or iron oxides

Pink Granite (Unakite-bearing or Epidote-bearing Granite)

Plutonic Igneous Rock (Granite)

Lapis Lazuli

Lazurite-dominant rock, (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2

Small green-gray pebble (likely serpentinite)

Serpentinite, composed mainly of serpentine-group minerals

Weathered quartz-rich rock fragments

Probable granite or granitic gneiss; quartz (SiO₂), feldspar, and mica

Quartz–pyrite-bearing vein rock, possibly gold-bearing

Quartz (SiO₂) with iron sulfides, chiefly pyrite (FeS₂), in altered host rock

Quartz-rich granite or granitic gneiss

Granite; primarily quartz (SiO₂), feldspar, and minor mica

Quartz-veined river pebble

Quartz-bearing metamorphic rock, possibly silicified schist or altered volcanic rock

Weathered quartz-rich metamorphic rock (probable quartzite)

Quartzite; predominantly microcrystalline quartz (SiO₂), with possible mica, feldspar, and iron-oxide impurities

Weathered granite or granitic gneiss

Granite; quartz + feldspar + biotite/hornblende, possibly weakly gneissic