This is a 10.7" tall amethyst cathedral geode from Minas Gerais, Brazil. It weighs 40 lbs and is full of large, light purple amethyst crystals surrounded by clear quartz. The base has been cut flat and the back of the geode has been strengthened with black resin as is done with all of these geodes
Nice big crystals with good terminations and a lot of sparkle in this specimen. An absolutely beautiful decorative piece.
Amethyst is a purple variety of quartz (SiO2) and owes its violet color to natural irradiation, iron impurities, and the presence of trace elements, which result in complex crystal lattice substitutions. It’s considered a semi-precious gemstone, and just two centuries ago was considered to have a value on par with diamonds, sapphires and rubies.
Much of the world’s amethyst comes from extensive deposits in Southern Brazil that have been heavily mined for about a century. The amethyst occurs in large cavities or geodes within volcanic rocks and the coloration and crystal size can vary greatly.