Migmatite
Image: <a href="//commons.wikimedia.org/wiki/User:Siim" title="User:Siim">Siim Sepp</a> (CC BY-SA 3.0)
Mineral NameMigmatite
Chemical FormulaNot applicable (rock, composed of multiple minerals)
Mohs HardnessVariable (typically 6-7 for felsic components, 2.5-3 for micas)
Streak ColorWhite to light gray
CleavageVariable (present in individual minerals like mica and feldspar, but not a property of the rock as a whole)
FractureUneven to conchoidal
Specific Gravity2.65
Colorsgray, white, dark gray
TransparencyOpaque
Type LocalitySaaremaa, Estonia
Mineral GroupMetamorphic rock
Usesbuilding material, decorative stone, geological study
Associated Mineralsquartz, feldspar, biotite, muscovite, amphibole, garnet
Raritycommon
Description
A large, rounded rock exhibiting distinct alternating light (leucosome) and dark (melanosome/paleosome) bands, often folded or contorted, giving it a streaky or wavy appearance.
Geological Context
Migmatites form under conditions of very high-grade regional metamorphism where partial melting of the protolith occurs, resulting in a rock with both igneous (melted) and metamorphic (unmelted) components.
