Defernite

Formula:  Ca₆(CO₃)_2-x(SiO₄)_x(OH)₇(Cl,OH)_1-2x      (x= 0.5)

Origin of name:  For Jacques Deferne, Swiss mineralogist

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell: a = 17.86, b = 22.77, c = 3.63

Colour:  Colourless, deep red to rose-brown

Diaphaneity:  Transparent

Luster:  Vitreous

Habit:  Fan-shaped forms, microscopic, or platy 0.5 x 2 cm

Hardness: 3

Specific gravity:  2.34 to 2.5

Cleavage:  2; {010} perfect, {100} distinct

Tenacity:

Streak:  Pinkish white

Synonyms/varieties:

Comments:  Dissolves in 1:1 HCl with effervescence