Mineral On Igneous Rock

Green glassy slag (often sold as “sea glass” or “green obsidian”)

Industrial vitreous slag; primarily amorphous silicate glass, composition variable

Quartz vein fragment

Quartz (SiO₂), likely milky quartz with iron-oxide staining

Milky Quartz (Quartz Vein)

Silicon Dioxide (SiO2)

Gneiss

Gneiss (Metamorphic Rock)

Tiny rounded brown mineral grain

Indeterminate; possibly iron oxide, garnet, or a weathered sulfide grain

Amygdaloidal Basalt

Amygdaloidal Basalt (Mafic silicate with secondary mineral inclusions)

Granite

Granite, a coarse-grained felsic intrusive igneous rock composed chiefly of quartz, feldspar, and mica

River Stone (likely Basalt or Greywacke)

Basalt with mineral veining

Weathered basalt (likely altered basalt)

Basalt, chiefly plagioclase feldspar and pyroxene, with possible chlorite/epidote alteration

Quartz (Small Fragment)

Silicon Dioxide (SiO2)

Quartz (Iron-stained)

Silicon Dioxide (SiO2)

Granite

Granite

Small weathered mineral/rock fragment

Uncertain from image; possibly quartz-rich sandstone or a feldspar-bearing rock

Quartz

Silicon Dioxide (SiO2)

Mineral and Rock Collection (Assorted)

Mixed collection including Quartz (SiO2), Jasper (SiO2 with impurities), Rose Quartz, and Aventurine

Granite

Intrusive Igneous Rock (composed primarily of quartz, alkali feldspar, and plagioclase)

Weathered granitic rock

Granite, likely quartz–feldspar–mica aggregate

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)

Likely polished or naturally smoothed pebble with a pale mineral patch

Undetermined; possibly a dark volcanic rock with a quartz or feldspar inclusion

Granite

Felsic intrusive igneous rock

Granite, likely weathered biotite granite

Phaneritic intrusive igneous rock composed chiefly of quartz, feldspar, and biotite amphibole

Weathered quartz-bearing rock, possibly calcite vein fragment

Indeterminate; likely quartz (SiO₂) with carbonate minerals such as calcite (CaCO₃)

Gneiss

Foliated Metamorphic Rock

Basalt or Slag

Extrusive Igneous Rock / Industrial Slag

Weathered granite fragment

Granite, predominantly quartz–feldspar–mica rock

Quartz Vein in Matrix

Silicon Dioxide (SiO2) within Rhyolitic or Granitic Matrix

Basalt with Iron Oxides

Mafic Igneous Rock (Mafite)

Rock specimen shown in a classroom identification activity

Undetermined; the pictured specimen may be a fine-grained, pinkish rock, but the image does not provide enough detail for a reliable identification

Milky quartz

Quartz (silicon dioxide, SiO₂)

Gneiss

Foliated Metamorphic Rock (Gneiss)

Basalt

Extrusive Igneous Rock

Granite

Granite

Granite cobble

Granite (Felsic Plutonic Rock)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Dark, iron-stained rock; exact identification uncertain

Possibly a fine-grained mafic igneous rock (basalt or diabase); image alone is insufficient for a reliable species-level identification

Pebble

Clast (specifically a granule or small pebble)

Basalt with Quartz/Calcite Veining

Basalt (principally Plagioclase and Pyroxene)

Granite

Phaneritic plutonic felsic rock (primarily Quartz, Feldspar, and Mica)

Basalt with Quartz Veins

Basalt (with SiO2 veins)

Dark gray-brown stone, likely basalt or fine-grained volcanic rock

Basalt (tentative; likely plagioclase–pyroxene rock)

Diorite

Intermediate plutonic igneous rock

Quartz-rich pegmatite (likely feldspar and quartz)

Granitic pegmatite composed mainly of quartz (SiO₂) and feldspars