General Information:
Chemical Formula:
KFe+++4(AsO4)3(OH)4·6-7(H2O)
Composition:
(Molecular Weight = 705.84 gm)
Potassium 5.54 % K
Iron 7.91 % Fe
Arsenic 31.84 % As
Hydrogen 2.57 % H
Oxygen 52.13 % O
Empirical Formula:
KFe3+(AsO4)3(OH)4·7(H2O)
Name Origin:
From the Greek, farmakon for "poison" and sideros for "iron."
Physical Properties:
Cleavage:
[100] Indistinct
Color:
olive green, emerald green, reddish brown, yellowish brown, or honey yellow.
Density:
2.8 - 3, Average = 2.9
Diaphaniety:
Subtransparent to subtranslucent
Habits:
Blocky - Crystal shape tends to be equant (e.g. feldspars)., Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Earthy - Dull, clay-like texture with no visible crys talline affinities, (e.g. howlite).
Hardness:
2.5 - Finger Nail
Luminescence:
None.
Luster:
Adamantine - Resinous
Streak:
yellowish green
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