Obsidian is mineral, but it is not a true mineral because, like glass, it is not crystalline; moreover, its composition is too variable to be classified as a mineral. It is sometimes classified as a mineraloid.
Although obsidian is generally dark in color, similar to mafic rocks such as basalt, the composition of obsidian is extremely felsic. Obsidian is primarily composed of SiO2 (silicon dioxide), typically 70% by weight or more.
Crystalline rocks of similar composition include granite and rhyolite. Since obsidian is metastable to the earth’s surface (over time the glass devitrifies, becoming fine-grained mineral crystals), obsidian is older than the Miocene Age is rare. Exceptionally ancient obsidians include welded Cretaceous tuff and partially devitrified Ordovician perlite. This transformation of obsidian is accelerated by the presence of water.
Although newly formed obsidian has a low water content, usually less than 1% water by weight, it gradually hydrates when exposed to the aquifer, forming perlite.
Obsidian a volcanic stone a result of rapid cooling of lava that spills onto the surface. The chess table of this chess set is made of obsidian stone handmade by Zlotoust masters, it undergo many process to create this beautiful and elegant chess pieces from selection of a blank to polishing.
Chess pieces have a pleasant weight to balance and can be able to stand during the play. The set includes 32 chess pieces, chess board, and a wooden box when ordered. The King measures 35 x 35 with a height of 90, the Queen measures 35 x 35 with a height of 100, and the Pawn measures 35 x 35 with a height of 53, while the chess board measures 370 x 370 and the tile measures 45 x 45.
Wrapping It Up
Pure obsidian usually has a dark appearance, although the color will vary depending on the impurities present. Iron and other transitional elements can give obsidian a dark brown to black color. Most black obsidians contain nanoinclusions of magnetite, an iron oxide.
Very few obsidian samples are almost colorless. In some stones, the inclusion of small radially agglutinated white crystals (spherulites) of the mineral cristobalite in the black glass produces a marbled or snowflake pattern (snowflake obsidian).
Obsidian can contain patterns of gas bubbles that remain from the lava flow, aligned along the layers created when molten rock flows before being cooled. These bubbles can produce interesting effects such as a golden glow (shiny obsidian). A rainbow-like iridescent sheen (fiery obsidian) is caused by inclusions of magnetite nanoparticles creating thin film interference.