Heulandite

Sample of colourless and red Heulandite crystals. The red Heulandite are euhedral tabular crystals and the colourless Heulandite are euhedral coffin-shaped crystals. Vitreous lustre on the colourless crystals with a more pearly lustre visible on the red crystals. Heulandite ((Ca,Na)(Al2Si7O18) x 6H2O) can be white, greyish, colourless, greenish or red in colour with a vitreous lustre that is pearly on the cleavage. Streak is colourless and hardness is 3 1/2 to 4. Cleavage is perfect in one direction. Heulandite usually occurs as coffin-shaped or tabular single crystals but can also be radiating aggregates, foliated, globular or granular in form.