All rocks & minerals

Pyrite-bearing rock (likely pyrite in a quartz or sulfide-rich matrix)

Pyrite, FeS₂; the gray host may be quartz, carbonate, or another sulfide-bearing rock

Blue chalcedony cabochon (probable)

Chalcedony, a cryptocrystalline variety of quartz; silicon dioxide, SiO₂

Rounded gray limestone pebble with a calcite vein

Calcitic limestone, composed predominantly of calcite (CaCO₃), locally cut by a white calcite vein

Granite pebble

Coarse-grained granitic rock, principally quartz, potassium feldspar, plagioclase feldspar, and biotite mica; likely biotite granite or weathered pegmatitic granite

Honey-colored chalcedony (possibly yellow/orange agate or carnelian)

Chalcedony, a microcrystalline variety of quartz; SiO₂. The color may result from iron-oxide inclusions. Exact identification is uncertain from a photograph alone.

Weathered pink granite cobble

Granite, likely biotite-bearing pink granite; exact variety cannot be confirmed from a photograph

Rounded pink granite pebble

Granite, a coarse-grained felsic intrusive igneous rock composed primarily of quartz, feldspar, and minor mica or amphibole

Dyed blue howlite (turquoise imitation), possibly dyed magnesite

Howlite: Ca₂B₅SiO₉(OH)₅; the vivid blue color is artificial dye. Exact identification is uncertain from the photograph alone.

Unakite

Unakite (epidote-bearing altered granite; mainly pink potassium feldspar, green epidote, and quartz)

Granite, possibly granodiorite

Coarse-grained felsic plutonic rock; chiefly quartz (SiO₂), potassium feldspar and plagioclase feldspar, with biotite and/or hornblende

Brecciated jasper, possibly rainforest jasper

Jasper: microcrystalline to cryptocrystalline quartz, SiO₂, commonly containing hematite, goethite, chlorite, epidote, and other iron- and manganese-bearing minerals

Brecciated jasper, possibly rainforest jasper or brecciated rhyolite

Brecciated microcrystalline quartz (SiO₂), commonly called jasper; the green portions may contain epidote, chlorite, or iron-bearing silicates, while red-brown areas are typically hematite or other iron oxides

Polymictic breccia, possibly volcanic breccia

Polymictic clastic breccia; likely a matrix-supported breccia containing lithic fragments, quartz, feldspar, and dark mafic minerals

Weathered porphyritic basalt

Basalt, likely plagioclase-phyric basalt; primarily a fine-grained aggregate of plagioclase feldspar, clinopyroxene, and possibly olivine or iron-titanium oxides

Polished black stone egg, probably black obsidian

Obsidian, a natural volcanic glass; composition primarily silica-rich glass (approximately SiO₂), with variable iron and other trace elements

Polished white chalcedony or milky quartz pebble

Chalcedony, microcrystalline quartz (SiO₂), possibly with iron-oxide staining or a minor mineral inclusion

Weathered, iron-stained rhyolite pebble (possibly rhyolitic volcanic breccia)

Rhyolite, a felsic volcanic rock; mainly quartz and alkali feldspar with minor plagioclase, altered mafic minerals, and iron-oxide staining

Weathered granite (feldspathic, iron-stained granite)

Granite; primarily quartz, potassium feldspar, plagioclase feldspar, and minor mica/amphibole. Exact identification is uncertain from a single photograph.

Polished white agate or chalcedony bead

Microcrystalline quartz (SiO₂), likely chalcedony/agate with iron-oxide staining or a brown mineral inclusion

Banded agate pendant (likely carnelian or brown-and-white chalcedony agate)

Agate, a banded variety of chalcedony; microcrystalline quartz, SiO₂, with iron-oxide coloration

Phyllite (possibly low-grade greenish slate)

Foliated metamorphic rock composed mainly of very fine-grained quartz, mica, and chlorite; approximate composition varies and has no single fixed chemical formula

Peacock ore (iridescent chalcopyrite, possibly bornite)

Chalcopyrite, CuFeS₂; the iridescent surface may be natural tarnish or artificial acid treatment. Similar material is bornite, Cu₅FeS₄.

Fuchsite

Chromium-rich Muscovite Mica

Probable amber fragment

Amber (fossilized plant resin; chiefly amorphous organic resin, commonly dominated by succinite)

Weathered granite cobble

Granite (quartz–feldspar–mica rock; commonly containing quartz, K-feldspar, plagioclase, and biotite)

Pale granite pebble (tentative identification)

Granite; a coarse-grained felsic intrusive igneous rock composed primarily of quartz and feldspar, with minor mica or amphibole

Mica schist, likely biotite–muscovite schist

Mica schist; predominantly quartz, feldspar, biotite and/or muscovite mica. Exact mineral composition cannot be confirmed from the photograph alone.

Banded gneiss, probably granitic gneiss

Foliated gneiss composed mainly of quartz (SiO₂), feldspar—orthoclase/microcline and plagioclase—and dark mica, commonly biotite K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Gneiss

Feldspathic biotite gneiss; a high-grade metamorphic rock composed mainly of quartz, feldspar, and mica

Tree Agate

Chalcedony (SiO2)

Agate

Silicon dioxide (Chalcedony), SiO2

Granite

Intrusive Igneous Rock

Jasper

Microcrystalline Quartz (SiO2)

Sandstone with Quartz Vein

Quartzose Sandstone with Hydrothermal Quartz

Granite

Felsic intrusive igneous rock

Malachite

Copper Carbonate Hydroxide, Cu2CO3(OH)2

Basalt Pebble

Extrusive Igneous Rock

Obsidian

Volcanic Glass (Amorphous silicon dioxide with trace impurities)

Granite

Felsic intrusive igneous rock

Granite

Granite

Unakite

Granite composed of pink orthoclase feldspar, green epidote, and colorless quartz

Cinnabar in Quartz

Mercury sulfide (HgS) in silicon dioxide (SiO2)