Stillbite on Apophyllite and Heulandite

Fragment of a Geode with yellowish "wheat sheaves" of Stilbite that have a vitreous lustre. These Stilbite crystals are on top of white vitreous Apophyllite that is granular and embedded with red coffin-like and parallel crystals of Heulandite. Stilbite (NaCa2Al5Si13O36 x 16H2O) can be white, greyish, yellowish, red or brown in colour. Lustre is vitreous and is pearly on cleavage. Streak is colourless and hardness is 3 1/2 to 4. Cleavage is perfect in one direction. Stilbite usually occurs as bladed aggregates that resemble "wheat sheaves" but can also be found as radial, globular, or tabular crystals (rare). Apophyllite (KCA4Si8O20(F,OH) x 8H2O) can be colourless, white, grey, greenish, yellowish or reddish. Lustre is vitreous and pearly on the cleavage. Streak is white and hardness is 4 1/2 to 5. Cleavage is perfect in one direction. Apophyllite usually occurs in cube-like or tabular forms that are square in cross section but can also occur as lamellar, granular or compact forms. Heulandite ((Ca,Na)(Al2Si8O18) x 6H2O) can be white, greyish, colourless, greenish or red in colour. Lustre is vitreous and 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 crystals but can also be radiating aggregates of nearly parallel crystals. Smallman Collection