Chemical composition -- Potassium aluminum silicate.
Color -- Colorless to yellowish or grayish.
Optics -- R.I 1.50.
Durability -- Hardness 5.5-6. Brittle.
Crystal structure -- Tetragonal.
Specific Gravity -- 2.47-2.50.
Sources -- Found in volcanic lava deposits around the world, but cuttable crystals are found only in Italy, and they are quite small. Leucite is seen only in fairly complete collections.