Biotite is a phyllosilicate mineral belonging to the mica group and is a common component of various igneous, metamorphic, and sedimentary rocks. It is characterized by its dark brown to black color and pearly to vitreous luster. Biotite forms thin, flexible sheets with a hexagonal or monoclinic crystal structure. Its perfect basal cleavage and flaky appearance make it easily identifiable among other minerals.


Biotite has a wide range of applications, primarily due to its heat resistance, electrical insulation, and flexibility. In the construction industry, it has been used as a filler in drywall and other building materials. Biotite is also utilized in the manufacturing of electrical insulators, high-temperature lubricants, and heat-resistant glass. Additionally, its unique optical properties make it useful for geological research and as a reference mineral in thin-section petrography.


Biotite is not generally considered a gemstone due to its opaque nature and tendency to cleave into thin sheets. However, it can occasionally be found as an inclusion in other gemstones, such as quartz and feldspar, contributing to unique visual effects and patterns.


Biotite is formed through various geological processes, including the crystallization of magma and the metamorphism of rocks rich in aluminum and potassium. It can also form as a result of hydrothermal alteration and weathering of other minerals, such as feldspar and hornblende.


Biotite can be found in a diverse range of rock types, including granites, gneisses, schists, and pegmatites. It is often associated with other minerals such as quartz, feldspar, and muscovite. Significant deposits of biotite can be found worldwide, with notable occurrences in the United States, Canada, Russia, Brazil, and Madagascar.


In metaphysical and spiritual practices, biotite is believed to have grounding and balancing properties. It is said to help individuals connect with their inner strength and wisdom, while promoting emotional healing and self-awareness. Biotite is also considered a stone of transformation, assisting in the release of old patterns and the discovery of new paths in life. Additionally, it is thought to enhance focus, concentration, and decision-making abilities.

LusterPearly to vitreous
Hardness (Mohs)2.5 – 3 
StreakWhite to grayish-white
ColorDark brown to black
CleavagePerfect basal cleavage
Specific Gravity2.7 – 3.3