Where is Boulder Opal found?

Boulder Opal occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.

Where to find Boulder Opal

Collecting tips

1. Look for Ironstone Formations. Boulder opal is exclusively found within ironstone. Prospecting should focus on areas with exposed ironstone outcrops, particularly those showing signs of weathering and fracturing.
2. Identify Opal Seams. Opal often occurs as thin seams or veins within the ironstone. Look for subtle flashes of color or milky white patches that indicate the presence of opal.
3. Examine Weathered Surfaces. Weathering can expose opal seams or reveal the characteristic 'potch' (common opal) that often accompanies precious opal. Look for areas where the ironstone has been naturally broken or eroded.
4. Use a Pick and Shovel. Mining for boulder opal typically involves hand tools to carefully extract the ironstone matrix containing the opal, as heavy machinery can damage the delicate opal seams.

Quick Check

Color:

Vibrant play-of-color (opal) against a dark brown/reddish-brown matrix (ironstone).

Luster:

Vitreous to waxy (opal), dull to earthy (matrix).

Streak:

White (opal), reddish-brown (ironstone).

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