Zircon

Formula: ZrSiO₄

Origin of name: from Arabic zarqun and Persian zar = gold, gun = colour

Crystal system: tetragonal

Crystal class: 4/m 2/m 2/m

Twinning: on {101}, geniculate; also on {011}

Unit cell: a = 6.604 Å, c = 5.979 Å

Colour: colourless, brown, green, gray, yellow, red

Diaphaneity: transparent to opaque if metamict

Luster: vitreous to adamantine

Habit: crystals short to long prismatic, or dipyramidal; sheaf-like or radial-fibrous aggregates; irregular grains

Hardness: 7.5

Specific gravity: 4.6 to 4.7

Cleavage: 2; {110} imperfect, {111} poor

Tenacity: uneven, chonchoidal, brittle

Streak:  white

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