Phlogopite (Gold Mica)
Mica group, Phlogopite · Mineral Specimen / Industrial Mineral
Crystal System
Monoclinic; commonly occurs as massive, foliated, or micaceous aggregates with a basal cleavage pattern.
Mineral Group
Silicates; Phyllosilicates (Mica Group)
Chemical Formula
KMg3(AlSi3O10)(OH)2
Formation Process
Metamorphic or Igneous; typically forms through the regional metamorphism of magnesium-rich limestones (dolostones) or in ultramafic igneous rocks.
About This Crystal
The specimen presents as a dense, micaceous mass with a brownish-gold to bronze color. It displays a characteristic sub-metallic to pearly luster with bright, reflective glitter-like surfaces caused by the flat faces of tiny mica flakes. It is translucent in thin sheets and opaque in massive form.
Physical Characteristics
Color: Bronze-brown or yellowish-brown; Streak: White; Cleavage: Perfect basal (1 plane), allowing thin, flexible sheets; SG: 2.7–2.9; Fluorescence: Weak or absent.
Optical Properties
Biaxial negative; refractive index roughly 1.56-1.61; exhibits pearly luster on cleavage faces and weak pleochroism in thin sections.
Hardness & Durability
Origin Region
Prominent sources include Canada (Ontario, Quebec), Russia (Siberia), Madagascar, and the USA (New Jersey). Found in magnesium-rich marbles and pegmatites.
Hardness & Durability
Mohs hardness: 2.0–2.5; very soft and can be scratched with a fingernail. Durability is low due to the ease of separation along cleavage planes.
Care & Maintenance
Clean only with a soft, dry brush or a slightly damp cloth. Avoid ultrasonic cleaners and harsh chemicals as water can seep between the layers and cause delamination.
Rarity & Value
Relatively common. Value is generally low for massive/foliated forms, though large, well-formed euhedral crystals are prized by mineral collectors.
Special Characteristics
The most notable feature is its perfect basal cleavage, which allows the mineral to be split into thin, flexible, and elastic sheets. It is also highly heat and electrically resistant.
Lore & History
Historically used as an electrical insulator and in high-temperature furnace windows. In metaphysical traditions, it is believed to assist in mental clarity and emotional flexibility, often associated with the Solar Plexus chakra.