Druzy Quartz (Smoky/Milky Quartz)
Silicon Dioxide (Quartz) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal/Hexagonal; specifically druzy coating on massive or botryoidal host rock
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (with trace Al, Fe, and irradiation for smoky coloring)
Formation Process
Hydrothermal: Secondary mineralization where silica-rich fluids precipitate into cavities in existing rock at low to medium temperatures.
About This Crystal
A dense crust of tiny, sparkling crystals (druzy) covering a rocky matrix. The specimen shows a mix of milky white and smoky grey-tan tones with a vitreous to dull luster. The texture is granular and the surface is uneven with multiple small cavities or vugs.
Physical Characteristics
Color: Gray, tan, white; Streak: White; Hardness: 7; Fracture: Conchoidal (on individual crystals); Luster: Vitreous sparkle on crystal faces, dull on matrix; Fluorescence: Usually inert but can show weak green or yellow under UV depending on impurities.
Optical Properties
Refractive Index: ~1.544-1.553; Birefringence: 0.009; Optical character: Uniaxial (+); Phenomena: Scintillation (sparkle) due to many small crystal faces reflecting light.
Hardness & Durability
Origin Region
Global commonality (Brazil, USA, Morocco); likely from a geode or vug in volcanic basalt or sedimentary limestone
Hardness & Durability
Mohs Hardness: 7; Excellent durability/toughness for quartz, though the druzy layer can be prone to 'shedding' or chipping if struck due to the small size of the crystals.
Care & Maintenance
Wash with warm soapy water using a soft brush to remove dust from crevices. Avoid ultrasonic cleaners if the matrix is porous. Generally stable in sunlight unless treated with artificial dye.
Rarity & Value
Common; Value is determined by coverage, sparkle, and the aesthetics of the matrix. Generally affordable as a decorative or collection-starter piece.
Special Characteristics
The primary feature is its 'druzy' habit, which creates a carpet-like sparkling effect across the surface. Potential for micro-inclusions of iron oxides (forming the yellowish patches).
Lore & History
Quartz has been used since antiquity for tools and talismans. In lore, druzy quartz is believed to amplify the energy of other stones and promote collective harmony. Historically, it was often mistaken for ice ('krystallos').