Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a> (CC BY 2.0)
amorphousuncommonSilicates
Opal
SiO₂·nH₂O
This image displays a piece of precious opal embedded within a light-colored sandstone matrix. The opal exhibits a vibrant play-of-color, showcasing flashes of green, blue, red, and orange against a translucent, whitish body.
Opal Physical Properties
Mohs Hardness
6Crystal System
amorphousLuster
vitreousStreak Color
whiteCleavage
noneFracture
conchoidalSpecific Gravity
2.1Colors
white, colorless, yellow, orange, red, green, blue, pink, brown, blackTransparency
translucentType Locality
White Cliffs Opal Field, New South Wales, AustraliaMineral Group
SilicatesUses
jewelry, collectorAssociated Minerals
quartzRarity
uncommonGeological Context
Formed in the Wallumbilla Formation during the Lower Cretaceous period, this precious opal occurs within quartzose sandstone, typically filling voids or fractures in sedimentary rocks. It forms from the precipitation of silica-rich solutions.
