What is Margarite?
Margarite is understated but elegant: pale pink or silvery plates show how aluminium-rich rocks reorganise during metamorphism. It is a rewarding companion to corundum and kyanite in a carefully documented mineral suite.
Mineralogy and crystal structure
Reference formula: CaAl4Si2O10(OH)2. Margarite is a calcium-rich dioctahedral mica. Its layered structure gives perfect basal cleavage and pearly surfaces; it commonly forms with corundum, kyanite, chloritoid and other aluminium-rich minerals. Margarite is classified with silicates and has a monoclinic crystal system. Typical hardness is 2.5–3.5 on the Mohs scale and specific gravity is approximately 2.9–3.1.
Colour, lustre and habit
Typical colours include pale pink, white, grey, green. The usual micaceous, foliated, platy habit and pearly, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Margarite forms in or is associated with aluminium-rich metamorphic rocks, corundum-bearing assemblages and hydrothermal alteration zones. Important documented localities include Austria, Switzerland, Italy, the United States, Canada and Brazil.
A pearly pink mica for metamorphic suites
Margarite is understated but elegant: pale pink or silvery plates show how aluminium-rich rocks reorganise during metamorphism. It is a rewarding companion to corundum and kyanite in a carefully documented mineral suite.
Collecting and care
Soft and perfectly cleavable: protect flakes from abrasion, water and pressure.
