Although not suitable for jewelry, apophyllite is a popular collector’s piece. Perhaps the whitest of all gems, cut, colorless specimens are so devoid of color they can appear almost silvery. This stone is not rare, but facetable material is quite scarce.
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The gemstones known as apophyllites belong to a solid solution series of minerals that includes fluorapophyllite-(K), fluorapophyllite-(Na), and hydroxyapophyllite-(K). Fluorapophyllite-(K) is the most commonly found type. The rarest, fluorapophyllite-(Na), crystallizes in the orthorhombic system, while the others form in the tetragonal system.
Apophyllite’s extremely perfect and easy cleavage makes it very fragile and dictates that gem cutters choose an orientation with the table of a faceted stone not perpendicular to the crystal’s long axis.
Radiation can turn colorless material green, but heating may reverse this process.
Mumbai (Bombay), Maharashtra, India produces colorless as well as intense, apple-green colored crystals, due to the presence of iron. These iron-rich apophyllites occur in magnificent crystal groups. However, facetable material is usually rare and smaller than the colorless variety. Many other sites in Maharashtra produce apophyllites.
Gem cutters seldom facet apophyllites. Furthermore, facetable rough greater than 10 carats in size is very rare. Stones faceted as curiosities are usually colorless. However, custom gem cutters have faceted the green Indian material.
You’re more likely to find apophyllites in mineral collections than in jewelry collections. In addition to perfect cleavage and relatively low hardness (4.5 to 5), this gem has great heat sensitivity. The heat from a jeweler’s torch may cause these gems to exfoliate. In other words, true to its etymology, apophyllite may lose flakes or “leaves” of material if heated.