Zeolite in Basalt
Basalt with Leucodacite or Zeolite (Heulandite/Stilbite) inclusions · Mineral Specimen / Geochemical Study Material
Crystal System
Often Monoclinic or Orthorhombic (Zeolites); the host rock is fine-grained Igneous (Basalt)
Mineral Group
Silicates (Tectosilicates for Zeolites; Mafic Silicates for host rock)
Chemical Formula
Commonly (Ca,Na)_{2-3}Al_3(Al,Si)_2Si_{13}O_{36}·12H_2O (Heulandite) within an Fe-Mg silicate matrix
Formation Process
Igneous/Hydrothermal: Formed as secondary minerals filling vesicles (gas bubbles) in cooling basaltic lava via hydrothermal fluid circulation.
About This Crystal
A dark, fine-grained, porphyritic or vesicular volcanic rock (basalt) containing white, translucent to opaque mineral clusters that fill pre-existing cavities. The matrix has a dull, earthy luster, while the inclusions show a pearly to vitreous luster.
Physical Characteristics
Color: Dark gray to black matrix with white inclusions; Streak: White; Cleavage: Good in one direction for zeolites; Fracture: Conchoidal to uneven; Density: ~2.1-3.0 g/cm³; Non-magnetic.
Optical Properties
Biaxial; Refractive Index: 1.48-1.50 (for Zeolites); Low birefringence; No significant pleochroism in these massive varieties.
Hardness & Durability
Origin Region
Notable regions include the Deccan Traps (India), Iceland, and the Pacific Northwest (USA) in volcanic flood basalts.
Hardness & Durability
Matrix hardness: 5-6 Mohs; Inclusion hardness: 3.5-4 Mohs. Low durability due to the fragility of zeolites.
Care & Maintenance
Clean only with room temperature water and mild soap; avoid ultrasonic cleaners and acids. Store in a dry environment to prevent dehydration of zeolite minerals.
Rarity & Value
Common; generally low price range ($5–$50 depending on size) unless featuring well-terminated large crystals.
Special Characteristics
Features amygdaloidal texture where minerals have filled gas vesicles; sometimes exhibits faint fluorescence under UV light depending on trace elements.
Lore & History
Historically used as a construction stone (basalt). In metaphysical traditions, zeolites are believed to be detoxifying stones that absorb negative energy and environmental pollutants.