Mineralogical Specimen

Probable weathered basalt or andesite

Fine-grained mafic to intermediate volcanic rock; commonly plagioclase ± pyroxene, amphibole, and iron oxides

Quartzite

Metamorphosed Quartz Sandstone (SiO2)

Granite

Granite (Felsic Plutonic Rock)

Hypersthene

Enstatite (Hypersthene variety), (Mg,Fe)SiO3

Charoite

Charoite (K(Ca,Na)2Si4O10(OH,F)·nH2O)

Granite

Intrusive Igneous Rock

Gneiss (specifically a granitic gneiss cobble)

Gneiss (high-grade regional metamorphic rock)

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Granite

Intrusive igneous rock composed mainly of quartz, alkali feldspar, and plagioclase

Gneiss

Gneiss

Uncertain polymict breccia or altered volcanic rock

Likely hydrothermally altered volcanic breccia; exact mineral identification requires testing

Granite

Phaneritic Igneous Rock (composed primarily of Quartz SiO2, Alkali Feldspar, and Plagioclase)

Mica Schist

Mica Schist (primarily Muscovite or Biotite)

Crushed Stone (Gravel/Aggregates)

Crushed rock aggregate (varied composition including Granite, Limestone, and Quartz)

Red Granite

Phaneritic Plutonic Rock (High Potassium Feldspar)

Weathered iron-rich rock, possibly basalt or ironstone

Indeterminate; likely Fe-oxide-bearing basaltic rock (commonly magnetite/hematite in a silicate matrix)

Chert (Green River Chert)

Microcrystalline Quartz (SiO2)

Prasiolite and Quartz Crystal Cluster

Quartz (SiO2); Prasiolite is a variety of Quartz

Small rounded pebble

Indeterminate lithic grain; likely weathered sandstone, iron-stained quartz-rich rock, or a concretion

Polished orbicular granite (likely K2-type granite)

Granite, chiefly quartz, alkali feldspar, plagioclase, and dark amphibole/biotite; possible epidote-rich orbicules

Mica Schist (with Golden/Biotite inclusions)

K(Mg,Fe)3AlSi3O10(F,OH)2 (Biotite), KAl2(AlSi3O10)(F,OH)2 (Muscovite)

Granite (Dioritic or Hornblende-rich)

Phaneritic Plutonic Felsic to Intermediate Igneous Rock

Weathered sandstone or siltstone

Clastic sedimentary rock, chiefly quartz and feldspar grains cemented by silica, iron oxides, or carbonate

Rhodonite-bearing metamorphic rock

Manganese-rich metamorphic rock, chiefly rhodonite (MnSiO₃), with quartz and manganese oxides

Sapphire

Corundum (Al2O3)

Iron-rich weathered stone, possibly hematite-rich ironstone

Hematite/goethite-bearing ironstone; predominantly Fe₂O₃ and FeO(OH)

Dendritic Agate (or Dendritic Opal)

SiO2 (for Agate), SiO2·nH2O (for Opal)

Granite

Intrusive Phaneritic Felsic Igneous Rock

Granite

Felsic intrusive igneous rock

Weathered iron-rich sandstone or ironstone

Ferruginous sandstone, likely limonite/goethite-cemented quartz arenite

Hypersthene

(Mg,Fe)SiO3 - Enstatite-Ferrosilite series

Chert (specifically Silex or Flint)

Microcrystalline Quartz (SiO2)

Weathered granite pebble

Granite, chiefly quartz (SiO₂), feldspar, and mica/amphibole

Hypersthene (or Enstatite/Ferrosilite)

Orthopyroxene series (Mg,Fe)SiO3 - specifically, historically hypersthene (intermediate member) now referred to as Enstatite (Mg-rich) or Ferrosilite (Fe-rich)

Drill Core Sample

Cylindrical Rock Core (Specific mineralogy varies by extraction site)

Rose Quartz

Silicon Dioxide (SiO2) with trace amounts of titanium, iron, or manganese

Desert Rose Fragment (Atypical) / Weathered Chert

Silicon Dioxide (SiO2) or Barium Sulfate (BaSO4) depending on exact mineralogy

Granite

Granite

Schist

Schist (various mineralogical compositions including mica, chlorite, talc, etc.)

Banded Gneiss

Gneiss (Metamorphic rock of variable mineralogy, often quartz-feldspar base)

Gneiss

Gneiss (a type of metamorphic rock)

Banded River Rock / Gneiss (highly weathered)

Gneiss