Breccia
Image: R12347 at English Wikipedia (Public domain)
Mineral NameBreccia
Chemical FormulaVariable (composed primarily of quartz, SiO2, and altered crocidolite fibers)
Mohs Hardness6.5
Streak ColorWhite
CleavageNone (for quartz); perfect (for crocidolite fibers)
FractureConchoidal
Specific Gravity2.65
Colorsgolden, reddish-brown, blue, grey
TransparencyTranslucent
Type LocalityNamibia, China
Mineral GroupSilicates
Usesjewelry, ornamental stone, collector's item
Associated Mineralsquartz, crocidolite, limonite, hematite
Description
This is a polished or tumbled piece of Pietersite, a brecciated chalcedony, displaying vibrant chatoyancy with swirling patterns of golden, reddish-brown, and blue-grey colors. Its surface is smooth and reflective, highlighting the fibrous inclusions.
Geological Context
Pietersite is a rare form of brecciated chalcedony, formed when crocidolite fibers are replaced by quartz, creating a unique chatoyant effect. It originates from areas where crocidolite-rich rocks have undergone metamorphism and subsequent brecciation.
