Laumontite
Laumontite is really a known member of the Zeolite Group of minerals that also includes Analcime, Barrerite, Chabazite, Epistilbite, Gmelinite, Goosecreekite, Heulandite, Leucite, Mordenite, Natrolite, Pollucite, Scolecite, Stellerite, Stilbite, Thomsonite, and Yugawaralite. Laumonite is just a “hydrated” mineral, meaning it includes water. Unfortunately, which means exposure to air causes it to lose some of its water which can destabilize crystals or gems and make them be powdery. When this happens, Laumontite dehydrates to become a mineral that is significantly different Leonhardite. Leonhardite is the real name for partially dehydrated, opaque Laumontite. Laumontite crystals and gems should really be sealed in an air container that is tight storage. Fortunately, the dehydration alteration is slow and a treasure or specimen can remain in good condition for several years if it is maintained precisely.
Leonhardite was named by Johann Reinhard Blum (1802-1883) in 1843 honoring Karl Ritter von Caesar Leonhard (1779-1862). Von Leonard was a tax administrator and assessor regarding the Grand Duchy of Frankfurt, and eventually, he became Professor of mineralogy at the University of Heidelberg, Germany.
Laumontite was originally named Laumonite (missing a “t”) in 1805 by Abraham Gottlieb Werner (1749-1817) in honor of François Pierre Nicolas Gillet Laumont (1747-1834), Inspector General of Mines, who discovered the mineral. The name was changed to its spelling that is present, in 1821 by Karl Ritter von Caesar Leonhard. Laumont’s birth name was François Pierre Nicolas Gillet. He took on the real name” of Laumont” to distinguish himself from their older cousin François Pierre Gillet of Renommière (1734-1813). Perhaps the mineral should are named Gilletite.
Laumontite circulation: relatively common. Well-crystallized specimens: from Huelgoat, Finistμere, France. From Sãcãrâmb (Nagyág), Romania. At St. Gotthard, Ticino, Switzerland. From Floitental, Zillertal, and other areas in Tirol, Austria. In Italy, from Baveno, Piedmont. From Poona plus in the Khandivali quarry, near Bombay, Maharashtra, India, large crystals. In the united states, exemplary crystals from the Pine Creek tungsten mine, Bishop, Inyo County, California; from Drain, Douglas County, Oregon; at Bergen Hill, Hudson County, and Paterson, Passaic County, brand new Jersey; into the Goose Creek quarry, Leesburg, Loudoun County, Virginia; on the Keweenaw Peninsula, Houghton and Keweenaw Counties., Michigan.
| Category: | Zeolite |
| Chemical Formula: | CaAl2Si4O12 • 4(H2O) |
| Hydrated Calcium Aluminum Silicate | |
| Molecular Weight: | 470.44 gm |
| Composition: | Calcium | 8.52 % | Ca | 11.92 % | CaO |
| Aluminum | 11.47 % | Al | 21.67 % | Al2O3 | |
| Silicon | 23.88 % | Si | 51.09 % | SiO2 | |
| Hydrogen | 1.71 % | H | 15.32 % | H2O | |
| Oxygen | 54.42 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals square prisms with steep oblique terminations, stout, commonly elongated, to 20 cm. Radiating, columnar, fibrous; in interlocking aggregates, massive. |
| Twinning: | On {100}, typically with terminal re-entrants. |
| Cleavage: | Perfect on {010}, {110} |
| Fracture: | Irregular/Uneven |
| Tenacity: | Brittle |
| Moh’s Hardness: | 3.0 – 4.0 |
| Density: | 2.23 – 2.41 (g/cm3) |
| Luminescence: | Fluorescent; weak white under SW and LW UV |
| Radioactivity: | Not Radioactive |
| Other: | Undergoes a partial loss of H2O on exposure to air. |
| Color: | White to gray, pink, yellowish, brownish, golden brown; colorless in thin section. |
| Transparency: | Transparent to translucent |
| Luster: | Vitreous to pearly on cleavages |
| Refractive Index: | 1.502 – 1.526 Biaxial ( – ) |
| Birefringence: | 0.007 – 0.012 |
| Dispersion: | Distinct; r < v; weakly inclined. |
| Pleochroism: | None |
