Celsian

Formula:  BaAl₂Si₂O₈

Origin of name:  For Anders Celsius, Swedish chemist and astronomer

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell:

Colour:  Colourless, white, yellow

Diaphaneity:  Transparent

Luster:  Vitreous

Habit:  Crystals short prismatic, prism faces prominent; massive

Hardness:  6 to 6.5

Specific gravity:  3.10 to 3.45

Cleavage:  3; {001} perfect, {010} good, {110} poor

Tenacity:

Streak:

Synonyms/varieties:

Comments:  Dimorphous with paracelsian; series with hyalophane and orthoclase