VS
Name
—
(Na,Ca,K)₁₋ₓ(V⁵⁺,V⁴⁺,Fe²⁺)₈O₂₀·4H₂O
Formula
—
Mineral Species
Entry type
—
Oxides & Hydroxides
Chemical class
—
Monoclinic
Crystal system
—
2.5–3
Mohs hardness
—
2.82
Specific gravity
—
Purplish blue-black
Streak
—
“Lusterous”. n = [2.05] (rule of Gladstone and Dale)
Luster
—
—
Cleavage
—
C2/m
Space group
—
Straczekite
Structural group
—
Cvu · Grandfathered
IMA
—
1933
Named in
—
Purplish blue-black to greenish black; olive-green to greenish yellow in thin fragments
Typical colors
—
Na · Ca · K · V · Fe · O · H
Elements
—