Antropogenic (Man Made Glass Byproduct)

Quartz-rich river pebble, likely milky quartz

Milky quartz (SiO₂), possibly a quartzite or quartz-rich silicate pebble

Quartz-rich rock, likely milky quartz vein material

Quartz (SiO₂), possibly iron-stained massive quartz with minor feldspar or mica

Polished mahogany obsidian (probable)

Volcanic glass; chiefly rhyolitic silica-rich glass (SiO₂), compositionally near rhyolite

Weathered quartz-rich rock, possibly pegmatite or quartzite

Quartz (SiO₂)-rich aggregate; exact identification is uncertain from the photograph

Obsidian

Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide)

Chert / Flint

Silicon Dioxide (SiO2)

Dark gray basalt or andesite cobble

Fine-grained mafic to intermediate volcanic rock; commonly plagioclase feldspar, pyroxene, and possibly olivine

Polished carnelian-rich agate (likely polyhedral jasper/chalcedony)

Microcrystalline quartz, SiO₂, with iron-oxide inclusions

Likely basalt

Basalt; fine-grained mafic volcanic rock, chiefly plagioclase and pyroxene with possible olivine

Pink Granite

Phaneritic Igneous Rock (Quartz-Feldspar-Mica)

Snowflake Obsidian

Vitreous Volcanic Glass (Siliceous Obsidian with Cristobalite inclusions)

Weathered quartz-rich pebble (likely milky quartz or quartzite)

Quartz, silicon dioxide (SiO₂); possibly quartzite, a metamorphic quartz rock

Milky quartz with iron-oxide staining and matrix

Quartz, silicon dioxide (SiO₂), likely massive quartz

Likely quartz-bearing mineral aggregate

Quartz (SiO₂), possibly mixed with mica or feldspar

Serpentinite

Serpentinite (composed primarily of serpentine-group minerals like antigorite, chrysotile, and lizardite; chemical formula varies but generally Mg3Si2O5(OH)4)

Chert or flint nodule

Microcrystalline quartz (SiO₂), likely chalcedony-rich chert

Tumbled brown translucent stone, likely quartz/jasper

Microcrystalline quartz (SiO₂), possibly iron-stained chalcedony or jasper

Weathered granite or granitic gneiss

Granite; chiefly quartz, alkali feldspar, plagioclase, and minor mica

Seraphinite

Clinochlore (Mg,Fe)5Al(AlSi3O10)(OH)8 - specific variety for Seraphinite due to its fibrous inclusions and chatoyancy.

Rounded quartz-rich pebble

Likely quartzite or quartz-rich sandstone pebble; SiO₂-dominant

Moonstone (specifically White Moonstone or Girasol Quartz)

Potassium aluminum silicate (KAlSi3O8)

Quartz pebble

Silicon dioxide (SiO2)

Light-colored quartz-rich stone, possibly milky quartz

Quartz (SiO₂), provisional identification

Vesicular basalt (likely weathered volcanic rock)

Basalt; primarily plagioclase feldspar, pyroxene, and commonly olivine

Quartz-rich rock fragment

Microcrystalline quartz (SiO₂), possibly chalcedony or quartz-bearing breccia

Possible weathered quartz-rich rock or iron-stained mineral fragment

Indeterminate; possibly quartz (SiO₂) with iron-oxide inclusions

Quartz-rich pegmatite (likely milky quartz with feldspar and mica)

Granite pegmatite; chiefly quartz (SiO₂), with feldspar and mica-group minerals

Tumbled quartz pebble (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Quartzite (Coldwater or Druzy Quartz over Quartzite)

SiO2 (Silicon Dioxide)

Mahogany Obsidian

Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions

Tumbled reddish sandstone pebble

Quartz-rich sandstone, likely ferruginous arkose or quartz arenite

Granite fragment

Granite

Granite

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

Weathered granite or granitic pegmatite cobble

Granite/granitic rock, composed mainly of quartz (SiO₂), feldspar, and minor biotite or other dark minerals; the reddish-brown areas may be iron-oxide staining or weathered accessory minerals

Obsidian

Volcanic glass (silica-rich rhyolitic melt; primarily SiO₂)

Dark metamorphic rock, likely hornfels or fine-grained basalt

Probable hornfels; commonly quartz–feldspar–mica with variable amphibole/pyroxene

Weathered quartz-rich pebble

Milky quartz, chiefly silicon dioxide (SiO₂), possibly with iron-oxide staining and minor feldspar

Quartz-bearing altered rock, possibly iron-stained quartz vein

Quartz (SiO₂) in a feldspathic/sericitized host, with iron-oxide staining

Tumbled carnelian (likely chalcedony)

Carnelian, orange-red cryptocrystalline quartz (SiO₂), a variety of chalcedony

Polished black stone, likely black obsidian

Obsidian (volcanic glass; primarily SiO₂)

Chert or heavily weathered flint

Microcrystalline quartz (SiO₂), likely chert/flint

Porphyritic Basalt or Diabase with Plagioclase Phenocrysts

Porphyritic Basalt or Diabase; Mineral: Plagioclase Feldspar