Volcanic Glass (Igneous)

Vesicular basalt (scoria-like lava rock)

Vesicular basalt; chiefly plagioclase, pyroxene, olivine, and volcanic glass

Black polished stone (possibly obsidian)

Obsidian (volcanic glass; composition typically rhyolitic)

Obsidian (likely black volcanic glass)

Obsidian; silica-rich, noncrystalline volcanic glass, typically rhyolitic (approximately 70–75% SiO₂)

Dark volcanic sand and basalt fragment

Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine

Milky Quartz

Silicon Dioxide (SiO2)

Mahogany Obsidian

Volcanic Glass with Hematite or Magnetite (SiO2 + Fe2O3)

Obsidian

Obsidian (Amorphous volcanic glass, SiO2 rich)

Obsidian (likely black volcanic glass)

Obsidian; naturally occurring rhyolitic glass, primarily SiO₂

Mahogany Obsidian

Volcanic glass (SiO2 with Hematite or Magnetite inclusions)

Polished black pebble, possibly obsidian

Volcanic glass (obsidian), likely; identification is tentative from the image

Pumice or vesicular volcanic tuff

Pumice: highly vesicular volcanic glass, chiefly rhyolitic to dacitic; possible tuff: lithified ash and pumice fragments

Polished snowflake obsidian

Obsidian, volcanic glass (SiO₂-rich rhyolitic composition) with cristobalite spherulites

Fine-grained gray rock, likely andesite or basalt

Aphanitic volcanic rock; probable basaltic-andesite (plagioclase ± pyroxene, minor iron oxides)

Polished black stone, likely obsidian or dark basalt

Volcanic glass (obsidian), possibly basalt; exact identification requires testing

Obsidian arrowhead

Volcanic glass; predominantly SiO₂, with minor feldspar, pyroxene, and iron oxides

Vesicular volcanic rock, likely scoria

Scoria (mafic volcanic vesicular basalt), chiefly plagioclase, pyroxene, olivine, and volcanic glass

Quartz Veined Diorite or Basalt

Crystalline Silicon Dioxide (Quartz) in Mafic Igneous Host (Basalt/Diorite)

Obsidian

Obsidian (Amorphous volcanic glass, predominantly SiO2)

Polished banded obsidian

Volcanic glass, predominantly SiO₂; likely banded or mahogany obsidian

Polished mahogany obsidian

Volcanic glass; primarily silica-rich rhyolitic composition (approximately 70–75% SiO₂)

Milky Quartz

Silicon Dioxide (SiO2)

Polished black obsidian (probable)

Volcanic glass; predominantly rhyolitic silica glass (approximately 70–80% SiO₂)

Polished black obsidian

Volcanic glass; predominantly rhyolitic silica glass (approximately 70–80% SiO₂)

Obsidian (likely Apache tear or flaked obsidian)

Volcanic glass; primarily rhyolitic silica glass (SiO₂-rich, non-crystalline)

Tektite (Indochinite)

Tektite (Natural silica glass)

Obsidian

Obsidian (Volcanic Glass, SiO2 + oxide impurities)

Polished black stone, likely obsidian

Volcanic glass; predominantly silica-rich rhyolitic glass (SiO₂), identification uncertain from the image

Yellow Chalcedony / Yellow Agate

Silicon Dioxide (SiO2)

Obsidian (black volcanic glass)

Obsidian; predominantly silica-rich volcanic glass, commonly rhyolitic (approximately 70–75% SiO₂)

Polished black-and-gold brecciated stone, likely sheen obsidian or brecciated jasper

Probable volcanic glass (obsidian), SiO₂, with iron-oxide or rhyolitic inclusions; exact identification is uncertain from the photograph

Black volcanic glass or basalt pendant

Likely basalt (fine-grained mafic rock), possibly obsidian (volcanic glass)

Rhyolite (possibly porphyritic and altered)

Volcanic felsic rock; primarily quartz, alkali feldspar, plagioclase, and volcanic glass, with iron-oxide alteration

Vesicular volcanic rock, likely pumice or scoria

Pumice (highly vesicular rhyolitic–dacitic volcanic glass) or scoria (vesicular basaltic rock)

Brecciated jasper (likely ocean jasper or rhyolitic jasper)

Silica-rich volcanic breccia; predominantly microcrystalline quartz/chalcedony (SiO₂) with iron-oxide and clay/mineral inclusions

Tumbled black stone, likely obsidian

Obsidian — volcanic glass, chiefly silica-rich rhyolitic composition

Obsidian-like volcanic glass (likely slag or natural obsidian)

Obsidian, primarily amorphous volcanic silica glass (approximately SiO₂); identification is uncertain from an image

Polished black stone, likely obsidian

Volcanic glass (obsidian), primarily silica-rich amorphous SiO₂

Obsidian

Obsidian (Volcanic Glass, SiO2 + impurity isotopes)

Red Scoria

Scoria (Vesicular Basalt/Andesite)

Obsidian

Obsidian (volcanic glass, amorphous silica rich rock)

Light-colored volcanic rock fragment, likely pumice or tuff

Pumice (vesicular volcanic glass) or volcanic tuff; not identifiable more precisely from the image

Scoria (vesicular volcanic rock)

Basaltic scoria; chiefly plagioclase, pyroxene, olivine, and iron-rich volcanic glass