AMETHYST, CRISTOBALITE and GOETHITE
A beautiful and fantastic specimen from Ametista do Sul, Rio Grande do Sul, Brazil.
Specimen size 6,7 x 5,4 x 3,8 cm. 109 grams.
The amethyst is not polished and have inclusions of cristobalite spheres and some goethite.
Cristobalite is a high-temperature polymorph of silica.
Some of the cristobalite spheres close to the surface of the amethyst crystal are covered with low-temperture water- clear quartz crystals with beautiful inclusions of goethite.