Laumontite is a mineral, one of the zeolite group. Its molecular formula is Ca(AlSi2O6)2 · 4H2O, a hydrated calcium-aluminium silicate. Potassium or sodium may substitute for the calcium but only in very small amounts.
It is monoclinic, space group C2/m. It forms prismatic crystals with a diamond-shaped cross-section and an angled termination. When pure, the color is colorless or white. Impurities may color it orange, brownish, gray, yellowish, pink, or reddish. It has perfect cleavage on [010] and [110] and its fracture is conchoidal. It is very brittle. The Mohs scale hardness is 3.5-4. It has a vitreous luster and a white streak.
It is found in hydrothermal deposits left in calcareous rocks, often formed as a result of secondary mineralization. Host rock types include basalt, andesite, metamorphic rocks and granites. It forms at a temperature of about 100 °C (212 °F), and becomes unstable above about 150 °C (302 °F), and so its presence in sedimentary rocks indicates that these have experienced intermediate diagenesis.[3]
The identification of laumontite goes back to the early days of mineralogy. It was first named lomonite by R. Jameson (System of Mineralogy) in 1805, and laumonite by René Just Haüy in 1809. The current name was given by K.C. von Leonhard (Handbuch der Oryktognosie) in 1821. It is named after Gillet de Laumont who collected samples from lead mines in Huelgoat, Brittany, making them the type locality.
Laumontite easily dehydrates when stored in a low humidity environment. When freshly collected, if it has not already been exposed to the environment, it can be translucent or transparent. Over a period of hours to days the loss of water turns it opaque white. In the past, this variety has been called leonhardite, though this is not a valid mineral species. The dehydrated laumontite is very friable, often falling into a powder at the slightest touch.
It is a common mineral, found worldwide. It can be locally abundant, forming seams and veins. It is frequently associated with other zeolites, including stilbite and heulandite. Notable occurrences are India; Paterson, New Jersey; Pine Creek, California; Iceland; Scotland; and the Bay of Fundy, Nova Scotia. Prehnite pseudomorphs after laumontite (epimorphs) have been found in India.
^National Audubon Society (1979). Field Guide to Rocks and Minerals. Alfred A. Knopf, Inc.
^Prothero, Donald R.; Schwab, Fred (2004). Sedimentary geology : an introduction to sedimentary rocks and stratigraphy (2nd ed.). New York: W.H. Freeman. p. 124. ISBN 0716739054.
Laumontite is a mineral, one of the zeolite group. Its molecular formula is Ca(AlSi2O6)2 · 4H2O, a hydrated calcium-aluminium silicate. Potassium or sodium...
with minerals such as datolite, calcite, apophyllite, epidote, stilbite, laumontite, and heulandite in veins and cavities of basaltic rocks, sometimes in...
association with powellite include molybdenite, ferrimolybdite, stilbite, laumontite and apophyllite. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols"...
mineralogical papers in the "Journal et Annales des Mines". The mineral laumontite, which Laumont discovered in the mines of Huelgoat, was named after him...
the dams along the Elan Valley. The quarry was the source of the first laumontite mined in Wales. It is operated by Hanson Aggregates. The town is served...
plagioclase feldspar. Also at greater depth in the zeolite facies, the zeolite laumontite replaces the zeolite heulandite and the phyllosilicate chlorite is common...
Name Symbol Name Symbol Name Symbol Name Symbol Name Symbol Laachite Laa Laumontite Lmt Lenoblite Lnb Linzhiite Lzh Lovdarite Lov Labuntsovite-Fe Lab-Fe Launayite...
he proposed the name "leonhardite" for partially dehydrated forms of laumontite. Die anorganische Chemie in ihren Grundzügen: dargestellt, 1839 – Inorganic...
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...
apophyllite, diopside, stilbite, tobermorite, clinohedrite, thaumasite, laumontite and wollastonite. The most common impurities include iron, magnesium and...
scolecite is commonly found alone or on stilbite and is covered with laumontite or colorless, pale green or white fluorapophyllite. It is also found in...
vermiculite. Mineral assemblages include kaolinite and montmorillonite with laumontite, wairakite, prehnite, calcite and chlorite. Phengite and adularia occur...
described leonhardite, a name given for a partially dehydrated, opaque laumontite. He was elected as a member to the American Philosophical Society in 1882...
there was significant metamorphic activity, enabling the formation of laumontite. The vegetation present in the area is primarily annual grasses and forbs...
silicate mineral, with which he made his habilitation in Göttingen, or the laumontite and the cordierite. In addition, Gmelin also analysed mineral waters and...
chalcedony or calcite, though zeolites, such as stilbite, mesolite and laumontite, are dominant towards Victoria Falls and in the lower Deka valley, and...
world, in metamorphosed basalts and diabases associated with prehnite and laumontite (Zolotukin et al., 1965). Julgoldite has also been found exposed in basalt...
(tobermorite, gyrolite and xonotlite) and zeolites (aluminosilicates: laumontite, mesolite, thomsonite, and analcime) also found in neighbouring localities...
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