20139 - Beautiful Purple Natural Amethyst Crystals Cluster Minas Gerais District - Brazil Cobaltoan calcite The rear edges of the

The rear edges of the trailing side can create a 'roll-over' rim or 'lip' where the ablating/melting material has started to roll-over onto the back side

The matrix has some fractures that have been glued together

Africa and North America

Kyrgyzstan

Nopcsa 1928

20139 - Beautiful Purple Natural Amethyst Crystals Cluster Minas Gerais District - Brazil Cobaltoan calcite The rear edges of theAmethyst is a purple variety of quartz (SiO2) and owes its violet color to irradiation, impurities of iron and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry.