Amygdaloidal Basalt with Zeolite filling
Basalt (Igneous Rock) with various zeolites (likely Natrolite or Analcime) · Mineral Specimen / Decorative Stone
Crystal System
Triclinic/Monoclinic matrix; zeolites are typically Orthorhombic or Isometric in habit
Mineral Group
Silicates; specifically Tectosilicates (zeolites) within a Mafic Volcanic matrix
Chemical Formula
Na2Al2Si3O10·2H2O (typical zeolite) within a silicate matrix (mainly Plagioclase and Pyroxene)
Formation Process
Igneous/Hydrothermal: Gas bubbles (vesicles) trapped in cooling lava are later filled by secondary minerals precipitated from percolating fluids
About This Crystal
A dark, fine-grained volcanic rock (matrix) containing rounded or petal-shaped white to cream-colored inclusions known as amygdules. The matrix is matte and opaque, while the inclusions show a pearly to vitreous luster.
Physical Characteristics
Matrix color: Dark grey to brown; Streak: Grey to greenish; Cleavage: None in matrix, varies in crystal fillings; Specific Gravity: 2.8 - 3.0; Matrix is non-fluorescent, but some zeolites may show weak green or yellow fluorescence.
Optical Properties
Matrix is opaque (non-refractive); mineral fillings are transparent to translucent with low refractive indices (n=1.47-1.50) and low birefringence.
Hardness & Durability
Origin Region
Common in volcanic terrains such as the Deccan Traps (India), Pacific Northwest (USA), or Iceland
Hardness & Durability
Matrix hardness: 5.0 - 6.0; Zeolite filling hardness: 3.5 - 5.5. Brittle toughness; the soft inclusions are prone to scratching and weathering.
Care & Maintenance
Avoid acidic cleaners which can dissolve carbonate/zeolite fillings; clean with warm soapy water only; store away from harder minerals to prevent scratching.
Rarity & Value
Common; primarily valued as geological curiosities or decorative river stones. Minimal commercial gemstone value.
Special Characteristics
Amygdaloidal texture (gas bubble fillings); the specimen shows 'amygdules' where secondary minerals have crystallized over geological time within the rock.
Lore & History
Historically used in construction and as road ballast. In metaphysical lore, zeolites within basalt are believed to assist in grounding (basalt) while facilitating the release of toxins or negative energy (zeolites).