Not A Rock

Serpentinite

Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony variety

Tumbled serpentine with dark magnetite/chromite matrix

Serpentinite; chiefly antigorite/lizardite, Mg3Si2O5(OH)4, with magnetite and possibly chromite

Basalt

Basalt

Gneiss

High-grade regional metamorphic rock (Foliated)

Granite

Granite (Phaneritic intrusive igneous rock)

Basalt

Basalt

Shale (Beach-worn)

Laminated Pelite (primarily clay minerals and quartz)

Unknown Tumbled Stone

Unknown (Too Blurry)

Conglomerate (puddingstone)

Polymict conglomerate; rounded pebbles and cobbles cemented in a finer matrix

Granite (likely weathered biotite granite)

Felsic intrusive igneous rock; mainly quartz, potassium feldspar, plagioclase, and biotite mica

Weathered granite or granitic gneiss pebble

Granite; primarily quartz, potassium feldspar, plagioclase, and mica

Likely gneiss

Gneiss, composed chiefly of quartz, feldspar, and mica/amphibole

Amber-bearing Coal/Sedimentary Rock

Bituminous coal or carbonaceous siltstone with Fossilized Tree Resin (C10H16O)

Likely basalt or vesicular volcanic rock

Basalt, possibly scoriaceous basalt; exact identification is uncertain from the photograph

Weathered porphyritic volcanic rock (likely basaltic andesite)

Porphyritic basaltic andesite; mineral assemblage likely plagioclase, pyroxene, and iron oxides

Herkimer Diamond

Quartz (Silica - SiO2)

Small rounded pebble, possibly quartz-rich stone

Indeterminate; likely quartz/quartzite or a weathered feldspathic pebble

Weathered greenstone pebble (probable serpentinite or altered basalt)

Serpentinite-group rock, commonly dominated by antigorite/lizardite; identification is uncertain from the photograph

Orange Quartz (or Carnelian Chalcedony)

Silicon Dioxide (SiO2)

Desert Rose (Gypsum Rose)

Calcium Sulfate Dihydrate (CaSO4·2H2O)

Rounded gray river cobble, likely quartz-rich sandstone or weathered granite

Indeterminate; possible granitic or feldspathic cobble (quartz–feldspar–mica aggregate)

Porphyritic Basalt or Porphyritic Andesite

Porphyritic Extrusive Igneous Rock

Sandstone (Weathered Cobble)

Clastic sedimentary rock (primarily SiO2)

Desert Varnish on Sandstone

Ferromanganese coating on Quartz Arenite

Vesicular Basalt (Scoria)

Aphanitic Mafic Igneous Rock (primarily Plagioclase and Pyroxene)

Quartzite with Feldspar and Mica (Granitic Gneiss Pebble)

Metamorphic Rock / Quartzite / Granitic Gneiss

Sandstone Pebble

Sandstone (Silicon dioxide-rich clastic sedimentary rock)

Quartzite Pebble (River Rock)

Metamorphic Quartzite (SiO2)

Granite (likely weathered granitic rock)

Granite; chiefly quartz (SiO₂), feldspar, and mica

Likely gneiss (banded metamorphic rock)

Felsic-to-intermediate gneiss; exact mineral identification requires closer examination

Granite pebble

Granite; chiefly quartz, feldspar, and mica

Quartz-Veined Slate or Greenstone

Metamorphic rock with quartz vein (SiO2)

Weathered granite or granitic gneiss

Granite: quartz, feldspar, and mica; possibly gneiss if the dark minerals are banded

Granite

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

Granite

Granite

Weathered Sandstone or Siltstone

Sedimentary Rock

Weathered quartz-rich pebble

Likely milky quartz (SiO₂), possibly a quartz-rich vein fragment

Tumbled brecciated jasper (likely ocean or mahogany jasper)

Jasper—microcrystalline quartz/chalcedony, SiO₂, with iron-oxide inclusions

Dalmatian Stone

Aplite (often incorrectly called Dalmatian Jasper)

Vesicular Basalt (Lava Rock)

Vesicular Basalt

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony variety