Apophyllite

Apophyllite is actually a small group of closely related phyllosilicate minerals (chiefly fluorapophyllite and hydroxyapophyllite) rich in water. Its name comes from the Greek 'apophyllizo', 'to flake off', because it crumbles and exfoliates when heated due to the loss of its water content.

It is hugely popular with collectors and crystal enthusiasts for its glassy transparency, well-formed pyramidal crystals, and the way it sparkles in clusters often perched on green stilbite or other zeolites.

Though too soft and brittle for everyday jewelry, fine apophyllite specimens, especially the rare green crystals from India, are highly sought after for display.

Apophyllite is a secondary mineral that forms in the cavities (vugs and vesicles) of basaltic lava flows, crystallizing from low-temperature hydrothermal solutions. It is part of the zeolite-associated mineral suite, even though it is not strictly a zeolite itself.

It typically grows alongside zeolites such as stilbite, heulandite, and scolecite, plus calcite and prehnite, lining gas pockets in volcanic rock.

The world's most celebrated specimens come from the Deccan Traps basalt quarries near Pune (Poona), India. Other localities include Brazil, Germany's Harz Mountains, Iceland, Scotland, Mexico, and the Lake Superior region of North America.

Look for glassy, colorless to white crystals shaped like cubes or rectangular prisms capped by a four-sided pyramid, often in sparkling clusters. The luster is vitreous on prism faces but distinctly pearly on the flat top (basal) face, due to perfect basal cleavage; this pearly sheen gives the 'fish-eye stone' nickname.

Hardness is only 4.5-5, so it is scratched by a steel knife. The streak is white and crystals are brittle.

Look-alikes include quartz (harder at 7, no perfect cleavage, hexagonal points), zeolites (different habits and lower density), and calcite (much softer, fizzes in acid, rhombic cleavage). Apophyllite's pyramid-tipped cubic crystals plus pearly basal sheen are the key tells.

Apophyllite is almost entirely a mineral-collector and metaphysical stone rather than an industrial or gem material. Its softness and fragility rule out most jewelry, so it is prized as cabinet specimens and crystal clusters for display.

Clear pyramidal points and clusters on green stilbite are especially valued by collectors. Occasionally water-clear crystals are faceted as curiosities for gem enthusiasts.

In crystal-healing practice apophyllite is described as a 'high-vibration' stone for clarity, meditation, and spiritual connection. These uses are spiritual beliefs and have no scientific basis, but they drive much of the demand for the Indian green and clear specimens.