Leucite

Here's a ping-pong ball sized specimen of the silicate leucite, featuring sharp (but distorted) trapezohedral faces and a light beige surface sitting in it's volcanic matrix. Another smaller crystal has seemingly pushed it's way into the main bigger crystal disrupting it's growth. These pseudo-trapezohedral crystals form directly in the cooling lava of volcanic rock. Only about five species of minerals come from the Roccamonfina Volcanic Complex in Italy including this one.