Ahlfeldite

Formula: NiSeO₃^.2H₂O

Origin of name:  for Friedrich Ahlfeld, German mineralogist

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 7.53 Å, b = 8.76 Å, c = 6.43 Å, b = 99.083°

Colour:  Brownish to reddish, apple-green

Diaphaneity: Transparent

Luster:  Vitreous

Habit:  Crystals minute, elongated; crystalline crusts

Hardness:  2 to 2.5

Specific gravity:  3.37

Cleavage:  2; (110) and (103) fair

Tenacity:

Streak: Light green

Synonyms/varieties:

Comments:  Series with cobaltomenite