9.17 Ct blue rectangle boulder opal

9.17 carats

Natural solid boulder opal

Yaraka mining region, Queensland, Australia

Length: 22.7 mm
Width: 8.2 mm
Depth: 3.9 mm

Opal ID 3290 is a Commercial Grade boulder opal.

Please find below a guide to our general grades. Please note that each opal is valued individually on multiple factors including brilliance, body tone, pattern, play-of-color, range of colors present, shape, size, presence or absence of inclusions, mining region and country of origin.

Top gem grade

Australian boulder opals of this grade are extremely rare. They score very high in most valuation factors, including, brilliance, colour, pattern and play-of-colour. They often also have a black or very dark body tone.

Gem grade

Australian boulder opals of this grade are rare. They score high in a combination of valuation factors, including, brilliance, colour, pattern and play-of-colour.

High commercial grade

Australian boulder opals of this grade are relatively more common than higher gem grades, but are still highly valued. Often, they score highly in one or more valuation factors and may have a ‘gem grade’ stripe or patch as part of the opal.   

Commercial grade

Australian boulder opals of this grade are relatively more common. Typically, they either score well in one or two factors, or are more ‘all-rounders’ scoring well in multiple factors. Again, they may have a higher-grade stripe or patch as part of the opal.