VS
Name
—
(Ca,REE)₄Y₂Al ₂(B₄Si₄O₂₂)(OH)₂
Formula
—
Mineral Species
Entry type
—
Silicates
Chemical class
—
Monoclinic
Crystal system
—
4.5–6.5
Mohs hardness
—
2.95–3.63
Specific gravity
—
—
Streak
—
Vitreous to dull
Luster
—
Poor on {100}, {010}
Cleavage
—
P2/a
Space group
—
Hellandite
Structural group
—
Hld-Y · Approved
IMA
—
1903
Named in
—
Nut-brown, brownish red, black, gray, green, yellow, cream, pinkish
Typical colors
—
Ca · REE · Y · Al · B · Si · O · H
Elements
—