Periclase
ID: 30
Periclase
Chemical Formula
MgO
Hardness (Mohs)
5.5 - 6
Crystal System
Isometric
Streak
White
Luster
Vitreous (glassy)
Diaphaneity
Transparent to translucent
Color
Colorless, gray, yellow, green, brown, black.
Crystal Habit / Mode of Occurrence
Isometric - Hexoctahedral; typically cubic crystals (often with rounded edges) or granular masses.
Fun Facts
Periclase is relatively unstable on Earth's surface and easily alters to brucite (Mg(OH)₂) in the presence of water, which is why it's rare in surface rocks. Common Uses: Used as a refractory material (high-temperature ceramics, furnace linings) due to its high melting point.