semiprecious gemstone of amethyst with calcite

south america brazil rio grande gramado texture abstract background rock mineralogy mineral ore deposit dig lode vein extraction underground subsurface mining geological gemology materials valuable february birthstone purple violet lapidary geode crystal druse lustre luster shiny amethystgrotto treasure vitreous calcite inclusion gem stone semiprecious gemstone quartz amethyst detail jewel polished magnificent inclusions cute european-influenced town southern highly sought tourists