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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 ...
Most commonly, volcanic glass refers to obsidian, a rhyolitic glass with high silica (SiO 2) content. [7] Other types of volcanic glass include the following: Pumice, which is considered a glass because it has no crystal structure. Apache tears, a kind of nodular obsidian.
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 ...
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And it's not just black and orange that represent All Hallow's Eve either. In recent years, green and purple have also risen in popularity, adding to the mix of colors that are linked to October 31.
In color theory, a shade is a pure color mixed with black. It decreases its lightness while nearly conserving its chromaticity. Strictly speaking, a "shade of black" is always a pure black itself and a "tint of black" would be a neutral gray. In practice, many off-black colors possess a hue and a colorfulness (also called saturation).
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