This is an awesome specimen! It's Amethyst from Brazil with a Calcite growing on it. The Amethyst formed as a geode, and has a lovely light purple shade to it. The calcite is white with three brown stripes running down the sides of it. The calcite also has a druzy layer on it, giving it a little bit more sparkle.
The piece measures ~10.7 x 11.4 x 8.9 cm