Zircon

Zircon crystal structure (tetragonal), CrystalMaker.

Zircon is a common accessory mineral of many igneous rocks. Pleochroic haloes are formed by damage to the crystal lattice of enclosing minerals by the radioactive decay of elements such as Th and U in zircon. These may be particularly noticeable in biotite grains in old granitic rocks.

Formula

Zr[SiO₄]

Structure

Orthosilicate

Crystal System

Crystal system: tetragonal (+)

Physical Properties

Colour in hand specimen: reddish brown, yellow, grey, green or colourless
Hardness: 7.5

Optical Properties

Colour in plane polarised light: colourless to pale brown
Pleochroism: very weak
Relief: high
Birefringence: 0.042-0.065; 3rd order green to 4th order green
Extinction: straight
Twinning: rare

Rock Specimens

L100 Alkali granite

Mineral Name

zircon