metamorphic
Migmatite
Migmatite (Mixed metamorphic-igneous rock)
Hardness: 6-7 on Mohs scale; Color: Banded or swirled black, grey, and white; Luster: Vitreous to dull; Crystal structure: Crystalline with coarse-grained leucosomes; Cleavage: Poorly defined; Specific Gravity: 2.6-2.9
- Hardness
- 6-7 on Mohs scale
- Color
- Banded or swirled black, grey, and white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Banded or swirled black, grey, and white; Luster: Vitreous to dull; Crystal structure: Crystalline with coarse-grained leucosomes; Cleavage: Poorly defined; Specific Gravity: 2.6-2.9
Formation & geological history
Formed under extreme temperature and pressure conditions during high-grade regional metamorphism. It represents a boundary state where a parent rock (protolith) begins to partially melt, creating a mixture of metamorphic rock and igneous melt.
Uses & applications
Used primarily as decorative stone in architecture, countertops, flooring, and as a durable construction aggregate. Its unique swirled patterns make it highly desirable for landscaping and ornamental masonry.
Geological facts
Migmatites are often referred to as 'bridging' rocks because they represent the link between metamorphic and igneous processes. The light-colored parts that melted are called leucosomes, while the dark, unmelted parts are melanosomes.
Field identification & locations
Identify in the field by looking for 'ptygmatic' (tightly folded) veins of quartz and feldspar within a darker gneissic matrix. Commonly found in Precambrian shield areas like the Canadian Shield or the Scandinavian Shield.
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