5/22/2004 · A marble is a small spherical object often made from glass, clay, steel, plastic, or agate.These balls vary in size. Most commonly, they are about 13 mm (1 ⁄ 2 in) in diameter, but they may range from less than 1 mm (1 ⁄ 30 in) to over 8 cm (3 in), while some art glass marbles for display purposes are over 30 cm (12 in) wide.Marbles can be used for a variety of games called marbles.Hematite, also spelled as haematite, is a common iron oxide with a formula of Fe 2 O 3 and is widespread in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe 2 O 3.It has the same crystal structure as corundum (Al 2 O 3) and ilmenite (FeTiO 3), with which it forms a complete solid solution at temperatures above 950 °C ...
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