Agate with Quartz Druzy
Silicon Dioxide var. Chalcedony (Agate) with Quartz crystals · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal/Hexagonal system; Agate is microcrystalline (cryptocrystalline) while the druzy center is macrocrystalline. Habit is massive and banded, often occurring in geodes.
Mineral Group
Silicates (Tectosilicate group, Quartz family)
Chemical Formula
SiO2 (Silicon Dioxide)
Formation Process
Hydrothermal/Igneous: Forms when silica-rich groundwater fills gas bubbles (vesicles) in volcanic lava. Layer-by-layer deposition creates the agate banding, while the final void fills with fine quartz druzy crystals.
About This Crystal
Tumbled heart-shaped specimen featuring concentric or 'fortification' banding in earthy brown and grey tones. The recessed center displays a 'druzy' surface consisting of a carpet of tiny, sparkling, transparent-to-white quartz crystals that create a glittering effect.
Physical Characteristics
Color: Varied bands of grey, brown, and white; Streak: White; Luster: Vitreous (glassy) on crystals, waxy on polished agate surfaces; Fracture: Conchoidal; Specific Gravity: 2.60–2.65; Fluorescence: Usually inert but can be weak green or yellow under UV.
Optical Properties
Chalcedony is translucent to opaque; Quartz crystals are transparent. RI: 1.544–1.553. Birefringence: 0.009. Agate is aggregate-polarizing.
Hardness & Durability
Origin Region
Brazil, Uruguay, and Madagascar are the primary sources for this high-grade banded material found in volcanic basalt cavities.
Hardness & Durability
Mohs Hardness: 6.5 to 7. Very durable and tough due to its microcrystalline structure, though the druzy surface can be prone to snagging or losing small crystals if hit.
Care & Maintenance
Clean with warm soapy water and a soft brush for the druzy area. Avoid ultrasonic cleaners and harsh chemicals. Store separately from other stones to prevent the druzy from scratching softer materials or being damaged by harder ones.
Rarity & Value
Common to Uncommon. Value is determined by the clarity of the banding, the sparkle and coverage of the 'druzy window,' and the quality of the lapidary carving. Most specimens are natural, though some may be dyed.
Special Characteristics
Features a 'druzy' window (a cavity of tiny crystals) and rhythmic banding. Shows no prominent optical phenomena like chatoyancy, but has a high glitter effect (scintillation) from the druzy surface.
Lore & History
Historically used in amulets and hardstone carvings since the Neolithic era. In traditional lore, agate is associated with grounding, stability, and protection. The druzy center is often marketed as a 'cave' for amplifying energy and promoting self-reflection.