This is a collector-grade natural Koroit boulder opal specimen, weighing 98.75 carats and measuring 29 x 18 x 25 mm.

Unlike typical cutting rough, this piece has been left completely natural due to its exceptional formation and sculptural presence.

Mother Nature has formed a distinctive nut-shaped nodule over ironstone, sitting on a natural potch base, with visible colour concentration at the junction where the formation developed.

This is a specimen piece — not just a cutting stone.

Key Features

• Weight: 98.75 carats

• Size: 29 mm x 18 mm x 25 mm

• Origin: Koroit, Queensland, Australia

• Type: Natural Boulder Opal Specimen

• Formation: Natural nodular “nut” overgrowth on ironstone

• Body Tone: Deep chocolate brown ironstone matrix

• Colour: Play-of-colour flash at formation join

• Pattern: Natural ring pattern visible near base

• Surface: Untouched natural formation

Why This Piece Is Special

• Rare sculptural morphology

• Clear geological story visible in the structure

• Ring pattern preserved in natural state

• Colour concentrated at structural junction

• Strong contrast between chocolate ironstone and flash

Many Koroit pieces are cut for jewellery.
Few are left intact when the natural formation is this distinctive.

This piece shows multi-stage silica deposition — base formation, colour seam development, and later nodular overgrowth — making it highly desirable for serious collectors of natural Australian opal specimens.

Cut or Specimen?

It would be possible to cut this stone, however doing so would permanently remove the unique natural morphology and ring structure.

For that reason, it is offered as a collector specimen in natural form.

Ideal For

• Advanced opal collectors

• Geological specimen collectors

• Display cabinet presentation

• Investment-grade Australian opal specimens