Metamorphic Or Igneous (Context Dependent)

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Sedimentary/Metamorphic Matrix

Native American Pottery Sherd

Black Star Diopside

Diopside (CaMgSi2O6) with Magnetite inclusions

Faceted Gemstones (Mixed)

Various (e.g., Corundum, Beryl, Quartz, or synthetic equivalents)

Unidentified gray stone

Likely quartz-rich stone; exact identification is not possible from the image

Polished peach aventurine or quartz

Likely quartz (SiO₂), possibly feldspar-rich aventurine

Milky Quartz

SiO2 (Silicon Dioxide)

Tumbled blue quartz (likely dyed quartzite or blue aventurine)

Quartz, silicon dioxide (SiO₂); blue coloration may result from inclusions or dye

Dalmatian jasper (polished stone beads)

Commercial “Dalmatian jasper”; typically a feldspar-rich rock with dark aegirine or arfvedsonite inclusions, not true jasper

Pyrite in Matrix (likely Quartz or Schist matrix)

Iron Sulfide (FeS2)

Likely rough blue-gray kyanite

Kyanite, Al₂SiO₅

Quartz

Silicon dioxide (SiO2)

Tumbled milky quartz (probable)

Quartz, silicon dioxide (SiO₂)

Blue-gray kyanite crystal

Kyanite, Al₂SiO₅

Blue Sapphire

Corundum (Al2O3 - Aluminum Oxide)

Blue aventurine or dyed blue quartz crescent

Quartz, silicon dioxide (SiO₂), likely aventurine quartz; exact identification requires testing

Exposed aggregate concrete (stone-chip surface)

Portland-cement concrete containing natural aggregate; not a natural rock

Tumbled limestone or marble

Calcite-rich carbonate rock; likely limestone (CaCO₃), possibly marble

Scoria

Scoria

Likely blue-green kyanite

Kyanite, Al₂SiO₅

Fuchsite or Green Mica Schist

K(Al,Cr)2(AlSi3O10)(OH)2

Polished blue-gray stone, likely labradorite or gneiss

Labradorite-bearing gneiss; plagioclase feldspar-rich rock

Tiny amber-colored crystal fragment

Indeterminate; possibly quartz, feldspar, mica, or a sulfide mineral

Labradorite-bearing gneiss or schist

Feldspathic gneiss/schist containing iridescent labradorite (plagioclase feldspar, NaAlSi₃O₈–CaAl₂Si₂O₈)

Blue kyanite in matrix

Kyanite, Al₂SiO₅

Sapphire

Corundum (Al2O3)

Black Tourmaline (Schorl)

Schorl (Complex sodium iron aluminum borosilicate)

Milky Quartz Pebble with Iron Inclusions

Silicon Dioxide (SiO2) with iron oxide impurities

Baked-clay ceramic fragment (likely brick or pottery)

Fired clay, primarily aluminosilicate minerals; not a natural rock

Greenstone / Greenschist

Greenschist (containing Chlorite, Epidote, Actinolite)

Wishing Stone

Greenschist or Basalt with Quartz/Calcite Vein

Weathered granitic rock (likely granite or granodiorite)

Granite–granodiorite; mainly quartz, feldspar, and mica/hornblende

Unidentified Rock Fragment

Unknown

Citrine

Citrine (Silicon Dioxide, SiO2)

Granite

Granite

Tumbled green aventurine (probable), with blue-gray tumbled stones

Aventurine quartz, SiO₂ with fuchsite or other mica inclusions; blue stones may be sodalite or dyed quartz

Rhodonite

Manganese silicate (Mn,Fe,Mg,Ca)SiO3

Veined gneiss

Felsic to mafic banded gneiss, chiefly quartz–feldspar–biotite/hornblende

Blue obsidian (likely carved volcanic glass)

Obsidian, naturally occurring silica-rich volcanic glass (composition commonly rhyolitic)

Dark mafic rock, likely basalt or amphibolite

Probable basalt (plagioclase feldspar + pyroxene ± olivine); definitive identification requires a fresh surface or thin section

Granodiorite (Gneissic Pebble)

Granodiorite displaying minor foliation

Raw Garnet (Hessonite / Spessartine)

Silicate mineral group (X3Y2(SiO4)3)