igneous
Sodalite in Matrix (often called Blue Marble or Sodalite-Syenite)
Sodalite-bearing Syenite / Na8Al6Si6O24Cl2 (Sodalite component)
Hardness: 5.5 to 6 on Mohs scale; Color: White to grey matrix with distinct royal blue or lavender-blue patches; Luster: Vitreous to greasy; Crystal structure: Cubic (isometric) for sodalite; Cleavage: Poor; Specific gravity: 2.14 to 2.4
- Hardness
- 5
- Luster
- Vitreous to greasy
Identified More igneous →
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Physical properties
Hardness: 5.5 to 6 on Mohs scale; Color: White to grey matrix with distinct royal blue or lavender-blue patches; Luster: Vitreous to greasy; Crystal structure: Cubic (isometric) for sodalite; Cleavage: Poor; Specific gravity: 2.14 to 2.4
Formation & geological history
Formed in silica-poor igneous rocks (alkaline rocks) such as nepheline syenites and pegmatites. It crystallizes from late-stage sodium-rich hydrothermal fluids. Usually Proterozoic to Phanerozoic in age.
Uses & applications
Used primarily for lapidary work, cabochons, beads, ornamental carvings, and architectural accents like tabletops or tiles. It is a popular collector's mineral due to its vibrant color.
Geological facts
Sodalite is often mistaken for Lapis Lazuli, but it lacks the gold-colored pyrite specks characteristic of Lapis. Many specimens exhibit fluorescence, glowing orange or yellow under long-wave UV light.
Field identification & locations
Identify in the field by its rich blue color and association with white feldspars/nepheline. Found commonly in Brazil, Canada (Bancroft, Ontario), Namibia, and Russia. Look for the absence of metallic flecks to distinguish from Lapis.
