Metamorphic (Low Grade)

Unakite

Epidote–orthoclase–quartz metamorphic rock

Biotite schist (probable)

Mica schist; chiefly quartz, feldspar, and biotite mica

Limonite (Iron Ore)

Limonite (an amorphous mixture of hydrated iron oxides, primarily FeO(OH)·nH2O)

Corundum (Sapphire variant)

Aluminium oxide (Al2O3)

Anthracite Coal

Anthracite

Pyrite-rich schist or phyllite

Quartz–mica schist/phyllite with disseminated pyrite (FeS₂)

Epidosite (Epidote-rich rock)

Epidosite (consisting primarily of Epidote: {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH))

Beryl (Emerald Variety)

Beryllium Aluminum Silicate (Be3Al2(SiO3)6)

Tiger's Eye

SiO2 (Quartz with inclusion of iron oxides)

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals usually (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)

Beryl (Emerald variety in host rock)

Be3Al2(SiO3)6 (Silicate mineral)

Anthracite Coal

Anthracite (Highly Metamorphosed Coal)

Greenstone / Chert

Cryptocrystalline Quartz (SiO2) or Altered Basalt

Likely slate or fine-grained metamorphic rock

Slate; predominantly microcrystalline quartz, mica, and clay minerals

Unakite (likely)

Epidote–pink feldspar–quartz rock; commonly termed unakite

Quartzite Pebble

Quartzite

Tumbled milky quartz pebble

Quartz (silicon dioxide, SiO₂)

Limonite

FeO(OH)·n(H2O)

Copper Ore (Malachite and Azurite on Host Rock)

Cuprite, Malachite, and Azurite dissemination in gangue

Gneiss (probable banded metamorphic rock)

Banded gneiss; typically quartz–feldspar–mica assemblage

Iron-stained quartzite or quartz-rich metamorphic rock

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

Gneiss

Banded gneiss; typically quartz–feldspar–mica assemblage

Anthracite coal

Anthracite; predominantly carbon (C), with minor mineral impurities

Green beryl, possibly emerald

Beryl (Be₃Al₂Si₆O₁₈), green variety; emerald if chromium/vanadium-colored

Serpentine-rich pebble

Serpentinite; chiefly serpentine-group minerals (chrysotile, lizardite, antigorite), commonly with magnetite and minor olivine/pyroxene

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals, Mg3Si2O5(OH)4)

Emerald

Beryl (Be3Al2Si6O18 with Chromium/Vanadium impurities)

Serpentinite

Serpentinite (composed primarily of mineral group (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4)

Fossil-bearing fine-grained sedimentary rock

Likely fossiliferous mudstone or shale; visible feature may be a plant fragment, trace fossil, or mineral vein

Emerald in Matrix

Beryl (Be3Al2(SiO3)6) with Chromium/Vanadium impurities

Likely basalt or mafic metamorphic rock

Basalt, predominantly plagioclase feldspar and pyroxene; possibly metamorphosed to amphibolite

Weathered schist or phyllite

Mica schist/phyllite, likely quartz–mica-rich metamorphic rock

Weathered quartz-rich rock, possibly milky quartz in altered host rock

Milky quartz (SiO₂), with probable iron-oxide staining and a fine-grained host matrix

White Jade

Nephrite (Ca2(Mg,Fe)5Si8O22(OH)2) or Jadeite (NaAlSi2O6)

Pyrite

Iron Sulfide (FeS2)

Gold Ore

Native Gold (Au) in Quartz or Silicate matrix

Vesicular Basalt with Zeolite

Mafic volcanic rock with Hydrated Aluminosilicate minerals (Zeolite group)

Prehnite

Prehnite Ca2Al2Si3O10(OH)2

Brecciated Jasper or Chert

SiO2

Weathered quartz-rich pebble

Quartz (SiO₂), possibly quartzite or quartz-bearing vein rock

Tumbled serpentine

Serpentine-group minerals, chiefly antigorite, lizardite, or chrysotile; approximate formula Mg₃Si₂O₅(OH)₄

Serpentinite

Serpentinite (complex of lizardite, chrysotile, and antigorite: (Mg,Fe)3Si2O5(OH)4)