Stilbite

The color is usually colorless or white, also yellow, brown, pink, salmon, orange, red, green, blue or black. The luster is generally vitreous, and on the perfect cleavage parallel to the plane of symmetry it is markedly pearly. The streak is white and crystals are transparent to translucent. The hardness is ​3 ⁄2 to 4 and the specific gravity 2.12 to 2.22. Cleavage is perfect on {010}, poor on {001}. The mineral is brittle, with a conchoidal or uneven fracture. It is not radioactive. Stilbite is biaxial (-) with refractive indices: Nx = 1.479 to 1.492, Ny = 1.485 to 1.500, Nz = 1.489 to 1.505 Nx = 1.484 to 1.500, Ny = 1.492 to 1.507, Nz = 1.494 to 1.513

Where sources give cell parameters for stilbite-Na, they are the same as those for stilbite-Ca. The unit cell can be considered as a monoclinic cell with β close to 130° and one formula unit per unit cell (Z = 1), or as a larger pseudo-orthorhombic cell with β close to 90° and Z = 2. Cell Parameters for the monoclinic cell: a = 13.595 to 13.69 Å, b = 18.197 to 18.31 Å, c = 11.265 to 11.30 Å, β = 127.94 to 128.1° a = 13.63 Å, b = 18.17 Å, c = 11.31 Å, β = 129.166° a = 13.60 to 13.69 Å, b = 18.20 to 18.31 Å, c = 11.27 Å, β = 128° Cell parameters for the pseudo-orthorhombic cell: a = 13.595 to 13.69 Å, b = 18.197 to 18.31 Å, c = 17.775 to 17.86 Å, β = 90.00 to 90.91° a = 13.595 to 13.657 Å, b = 18.197 to 18.309 Å, c = 17.775 to 17.842 Å, β = 90:05 to 90.91° (Z is doubled to Z = 4 because the formula unit halved to NaCa2Al5Si13O36.14H2O) a=13.69 Å, b=18.25 Å, c=11.31 Å, β =128.2° a = 13.60 to 13.69 Å, b = 18.20 to 18.31 Å, c = 17.78 to 17.86 Å, β = 90.0 to 90.91° The framework of stilbite is pseudo-orthorhombic with the open channels typical of zeolites. It has 10-member rings and 8-member rings forming channels parallel to a and pseudo-orthorhombic c respectively.

Stilbite is a type of zeolite, which makes it a good chemical filter. This mineral can be found in water filters and is particularly well-suited for separating hydrocarbons in petroleum refining. Stilbite is also a popular mineral amongst collectors for its unique hourglass and wheat sheaf structures.

At one time heulandite and stilbite were considered to be identical minerals. After they were found to be two separate species, in 1818, the name desmine ("a bundle") was proposed for stilbite, and this name is still employed in Germany. The English name "stilbite" is from the Greek stilbein = to shine, because of the pearly luster of the {010} faces.

Stilbite is abundant in the volcanic rocks of Iceland, Faroe Islands, Isle of Skye, Bay of Fundy, Nova Scotia (where it is the provincial mineral), northern New Jersey and North Carolina. Salmon-pink crystals occur with pale green apophyllite in the Deccan Traps near Mumbai (Bombay) and Pune, India; white sheaf-like groups encrust the calcite (Iceland-spar) of Berufjord near Djupivogr in Iceland; brown sheafs are found near Paterson, New Jersey in the United States; and crystals of a brick-red color are found at Old Kilpatrick, Scotland.

Iceland is generally considered to be the type locality for stilbite-Ca. It is presumed to be the Helgusta Iceland Spar Mine, along Reydarfjordur. Excellent white bow ties of stilbite are found here on calcite and quartz, associated with heulandite and laumontite in cavities.

The type locality for stilbite-Na is Cape Pula, Pula, Cagliari Province, Sardinia, Italy. Small, lustrous, white or pink, pointed blades of stilbite-Na, and formless masses, up to 5 cm in diameter, have been found there, covering a thin crust of reddish heulandite in large fractures and cavities in the highly weathered volcanic andesite or rhyolite.

The Tertiary Deccan basalts of western India are the most prolific sources of stilbite in the world. Stilbite is the most abundant zeolite in the tholeiitic basalt plateaux near Nasik and Pune and decreases in abundance toward the coast at Mumbai.

Stilbite shows a wide variation in exchangeable cations: silicon and aluminium ions occupy equivalent sites and can substitute for each other. Since silicon and aluminium have a different charge (Si and Al) the ions occupying the sodium/calcium site have to adjust to maintain charge balance. There is a continuous series between stellerite, whose formula can be written as Ca4(Si28Al8)O72·28(H2O), and stilbite, and another continuous series between stilbite and barrerite, Na8(Si28Al8)O72·26(H2O). Epistilbite is a distinct zeolite species unrelated to stilbite.

At one time heulandite and stilbite were considered to be identical minerals. After they were found to be two separate species, in 1818, the name desmine ("a bundle") was proposed for stilbite, and this name is still employed in Germany. The English name "stilbite" is from the Greek stilbein = to shine, because of the pearly luster of the {010} faces.

Stilbite is believed to provide a grounding force for spiritual energy and help a person on their spiritual journey. It provides protection in both the physical world and the spiritual realm, and is believed to expand consciousness of other dimensions. It can be helpful in matters of sleep, offering a calming balance for an overstimulated mind and encouraging relaxation.