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2. Obsidian - Wikipedia

   en.wikipedia.org/wiki/Obsidian

   In some stones, the inclusion of small, white, radially clustered crystals (spherulites) of the mineral cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being ...

3. Lithophysa - Wikipedia

   en.wikipedia.org/wiki/Lithophysa

   These rocks are usually found within obsidian or rhyolite lava flows. [2] Lavas low in feldspar minerals may produce a version known as snowflake obsidian . These cavities are believed to be caused by expanding gases in tuffs and rhyolitic lavas before solidification. [ 1 ]

4. Spherulite - Wikipedia

   en.wikipedia.org/wiki/Spherulite

   Spherulites in rhyolitic ash, Hailstone Trail, Echo Canyon, Chiricahua Mountains, Arizona Spherulite markings on snowflake obsidian Photomicrograph of rhyolite, showing spherulitic texture (brown, between grey to white crystals) In petrology, spherulites (/ ˈ s f ɛr ʊ l aɪ t s, s f ɪər-/) are small, rounded bodies that commonly occur in ...

5. Apache tears - Wikipedia

   en.wikipedia.org/wiki/Apache_tears

   Apache tears are rounded pebbles of obsidian or "obsidianites" composed of black or dark-colored natural volcanic glass, usually of rhyolitic composition and bearing conchoidal fracture. Also known by the lithologic term marekanite , this variety of obsidian occurs as subrounded to subangular bodies up to about 2 in (51 mm) in diameter, often ...

6. Glass Buttes - Wikipedia

   en.wikipedia.org/wiki/Glass_Buttes

   Examples of Glass Buttes obsidian. The Glass Buttes area offers a number of recreational opportunities including rock collecting, hiking, camping, hunting, and nature study. [4] Of these activities, rock collecting is the most popular. The buttes have one of the largest and most diverse deposits of obsidian in the world.

7. Cristobalite - Wikipedia

   en.wikipedia.org/wiki/Cristobalite

   Cristobalite occurs as white octahedra or spherulites in acidic volcanic rocks and in converted diatomaceous deposits in the Monterey Formation of the US state of California and similar areas. The micrometre-scale spheres that make up precious opal exhibit some X-ray diffraction patterns that are similar to that of cristobalite, but lack any ...