Dendritic Opal
Amorphous Hydrated Silica (Opal) with Manganese Oxide inclusions · Semi-Precious Gemstone / Collector Mineral
Crystal System
Amorphous (Non-crystalline); typically occurs in massive or botryoidal forms within volcanic rock cavities or sedimentary layers.
Mineral Group
Silicates; Tectosilicate (Mineraloid)
Chemical Formula
SiO2 · nH2O + Mn (Manganese inclusions)
Formation Process
Formed through the precipitation of silica-rich water at low temperatures. Tree-like 'dendritic' patterns are formed by manganese or iron oxides seeping into cracks and crystallizing as the silica hardens.
About This Crystal
Tumbled stone featuring a creamy off-white or light gray base with dark, mossy or tree-like black inclusions. Luster is vitreous to waxy, and the transparency is mostly opaque with slight translucency at the edges.
Physical Characteristics
Color: White, gray, black; Streak: White; Cleavage: None; Fracture: Conchoidal to uneven; Specific Gravity: 1.9–2.3; Tenacity: Brittle; Fluorescence: May show weak green or white under UV.
Optical Properties
Refractive Index: 1.44-1.46 (Singly Refractive); No pleochroism or dispersion; Lacks the 'play of color' (opalescence) found in precious opal, instead showing 'common opal' features.
Hardness & Durability
Origin Region
Madagascar, Mexico, Australia, and the USA. Commonly found in low-temperature hydrothermal environments and weathering volcanic rock.
Hardness & Durability
Mohs Hardness: 5.5 to 6.5. Toughness is poor due to high water content; sensitive to thermal shock and knocks. Durable enough for pendants but risky for rings.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and steam. Keep away from intense heat and direct sunlight to prevent dehydration/cracking. Store separately from harder stones like quartz or sapphire.
Rarity & Value
Common; Value is determined by the complexity and beauty of the dendritic patterns. Typically affordable ($5–$30 for small tumbled pieces). Inclusions are natural and not usually treated.
Special Characteristics
Presence of manganese dendrites (pseudofossils) that resemble plant life or landscapes. This specimen specifically exhibits 'merlinite-like' patterning of high-contrast black and white.
Lore & History
Historically used by various cultures as a talisman for 'growth' due to its plant-like appearance. In modern crystal healing lore, it is believed to be a stone of duality, balancing light and dark, and is associated with the Crown and Third Eye chakras for spiritual connection.