Hydrotalcite

Formula:  Mg₆Al₂(CO₃)(OH)₁₆ ^. 4H₂O

Origin of name:  From Greek hydor = water and talc

Crystal system:  Hexagonal

Crystal class:  -3 2/m

Twinning: 

Unit cell: 

Colour:  White

Diaphaneity:  Transparent

Luster:  Pearly or waxy

Habit:  Massive, foliated, lamellar, or fibro-lamellar

Hardness:  2

Specific gravity:  2.06

Cleavage:  1; {0001} perfect

Tenacity: 

Streak:  White

Synonyms/varieties:

Comments:  Dimorphous with manasseite; greasy feel