mineral

Dendritic Opal (Common Opal)

Amorphous Hydrated Silica (SiO2·nH2O) with Manganese or Iron Oxide inclusions

Hardness: 5.5-6.0 on Mohs scale; Color: Milky white to cream base with black or brown tree-like inclusions; Luster: Vitreous to waxy; Crystal Structure: Amorphous (non-crystalline); Cleavage: None; Specific Gravity: 1.9-2.3

Hardness: 5
Luster: Vitreous to waxy

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich water seeping into cracks and cavities within igneous or sedimentary rocks. The 'dendritic' patterns are formed by the precipitation of manganese or iron oxides during the opal's solidification. It doesn't have a specific geological age as it forms in various environments through history.

Uses & applications

Primarily used in jewelry as cabochons, beads, and tumbled stones. Highly valued by collectors for the unique, 'organic' patterns that resemble landscapes or plants. Used in metaphysical practices for its purported grounding properties.

Geological facts

Unlike 'precious opal', dendritic opal is a 'common opal', meaning it lacks the play-of-color (opalescence). The name 'dendrite' comes from the Greek word 'dendron', meaning tree, referring to the branching patterns of the mineral inclusions.

Field identification & locations

Identify in the field by its waxy texture, lack of crystal faces, and characteristic branching inclusions. Common locations include Australia, Brazil, Mexico, and the USA (specifically Nevada and Oregon). It feels lighter than quartz or chalcedony of the same size.

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