Natrolite, Mesolite, and Scolecite are fibrous or elongated zeolite minerals. Faceted gems are almost always elongated emerald cuts or step-cuts.
All three zeolites form elongated crystals; faceted gems are almost always, therefore, elongated emerald- or step-cuts. The New Jersey natrolites are by far the largest known faceted gems in this group. All three minerals are relatively fragile and soft, have good cleavage, and are white and more or less uninteresting, except for rarity. Compact masses, cut into cabochons, might be more durable due to interlocking of the fibers. The minerals can readily be distinguished on the basis of optical properties.
Natrolite occurs in cavities in basalts and other dark igneous rocks. Scolecite occasionally forms in schists and contact zones at limestones. Natrolites were known only in stones under 1 carat until the Bound Brook, New Jersey, find. Some of these crystals cut flawless gems over 20 carats.
Mesolite is never found in large transparent crystals. Faceted gems are thus very rare, although the possibility exists that larger crystals could be found one day. Fibrous material cuts fine catseye gems, but these also are small and fragile.
Scolecite is also rare in facetable crystals; areas of some of the large Indian and Brazilian material might cut gems in the 5-10 carat range, but these specimens are in museums and will not be cut. Other stones would likely be in the 1-3 carat range and colorless.
This solid-solution of the Zeolite group forms as slender or acicular prismatic crystals. Except for its rarity, Natrolite is usually an uninteresting white colour (sometime colourless, gray, yellowish, reddish). It has only been reported occurring in the Ice River area south-east of Golden.