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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 ...
They can have an average diameter 5–20 centimetres (2.0–7.9 in), [3] but can be much larger (for example, 300–370 centimetres (10–12 ft) at Silver Cliff in Colorado). Lithophysae are also related to the spherulites found in obsidians on the Italian island of Lipari , in Yellowstone National Park , and other places.
The snowflake is often a traditional seasonal image or motif used around the Christmas season, especially in Europe and North America. As a Christian celebration, Christmas celebrates the incarnation of Jesus , who according to Christian belief atones for the sins of humanity; so, in European and North American Christmas traditions, snowflakes ...
For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have very different properties. For example, diamond is the hardest substance known, while graphite is so soft that it is used as a lubricant.
Obsidian hydration dating (OHD) is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian.. Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping, or breaking off pieces in a controlled manner, such as ...
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Cristobalite (/ k r ɪ ˈ s t oʊ b ə ˌ l aɪ t /) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, Si O 2, but a distinct crystal structure.
A mineraloid is a naturally occurring substance that resembles a mineral, but does not demonstrate the crystallinity of a mineral. Mineraloid substances possess chemical compositions that vary beyond the generally accepted ranges for specific minerals, for example, obsidian is an amorphous glass and not a true crystal; lignite is derived from the decay of wood under extreme pressure ...