mineral

Dendritic Opal (Merlinite)

Hydrated Silica with Manganese/Iron oxide inclusions (SiO2·nH2O)

Hardness: 5.5-6.5 (Mohs scale); Color: Creamy white or milky base with black or green tree-like inclusions; Luster: Vitreous to waxy; Crystal Structure: Amorphous; Cleavage: None

Hardness: 5
Luster: Vitreous to waxy

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 5.5-6.5 (Mohs scale); Color: Creamy white or milky base with black or green tree-like inclusions; Luster: Vitreous to waxy; Crystal Structure: Amorphous; Cleavage: None

Formation & geological history

Formed as silica-rich water seeps into cracks and cavities in volcanic rocks. The 'branching' patterns are created by the crystallization of manganese or iron oxides during the cooling process.

Uses & applications

Predominantly used as a gemstone for jewelry (cabochons), lapidary carvings, and in metaphysical collections for its aesthetic 'landscape' appearance.

Geological facts

Although called 'opal', dendritic opal is technically a form of common opal that does not exhibit 'play-of-color'. The black patterns are often mistaken for fossilized plants (ferns), but they are strictly mineral growths.

Field identification & locations

Identified in the field by its distinctive moss-like or tree-like dark patterns against a white opaque background. Commonly found in Australia, Mexico, and Madagascar. Collectors look for high contrast and intact 'forest' patterns.

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