Granite Pegmatite
Igneous Rock / Mineral Assemblage (Quartz, Feldspar, Tourmaline/Biotite) · Mineral Specimen
Crystal System
Multi-system aggregate (Quartz is Trigonal, Feldspar is Monoclinic/Triclinic, Tourmaline is Trigonal)
Mineral Group
Silicates (Tectosilicates and Cyclosilicates)
Chemical Formula
Complex silicate mixture primarily consisting of SiO2 (Quartz), KAlSi3O8 (Feldspar), and complex cyclosilicates (Tourmaline)
Formation Process
Igneous crystallization from silica-rich magmas and volatile-rich pegmatitic fluids cooling slowly deep within the Earth's crust
About This Crystal
An intergrown crystalline rock specimen featuring a contrasting matrix of translucent to white quartz and feldspar heavily dotted with dark, lustrous, tabular to prismatic black mineral inclusions, likely tourmaline or biotite mica
Physical Characteristics
Colors include white, grey, and deep black; streak is white; vitreous to sub-metallic luster on the dark crystal faces; uneven to conchoidal fracture; specific gravity ranges around 2.6 to 2.8; highly brittle
Optical Properties
Varies by constituent minerals; quartz and feldspar are doubly refractive with low birefringence; dark inclusions show strong absorption and pleochroism
Hardness & Durability
Origin Region
Worldwide, commonly found in continental shields, mountain building zones, and major pegmatite fields such as Brazil, Madagascar, and the United States
Hardness & Durability
Composite hardness ranging from 6 to 7 on the Mohs scale due to the dominant quartz and feldspar components; moderate toughness; susceptible to thermal shock
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid harsh acids or prolonged soaking; store away from softer stones to prevent scratching
Rarity & Value
Common; value depends on the aesthetic contrast of the mineral assemblage, crystal size, and overall specimen cleanliness, generally affordable for collectors
Special Characteristics
Exhibits a striking salt-and-pepper matrix contrast with distinct euhedral to subhedral dark crystalline inclusions set against a lighter quartz-feldspar background
Lore & History
Used historically as a durable building and monumental stone; in modern metaphysical practices, it is believed to combine the grounding stability of earth elements with the amplifying clarity of quartz, though these are traditional beliefs and not scientifically proven