Last updated
Category tectosilicate
(repeating unit)
Strunz classification 9.GA.10
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Color colorless, white, beige, and pink
Cleavage perfect on {010}; good on {100}
Mohs scale hardness 5-5 12
Luster vitreous, pearly
Streak white
Diaphaneity transparent to translucent
Specific gravity 2.23 - 2.29

Thomsonite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named thomsonite-Ca and thomsonite-Sr. Thomsonite-Ca, by far the more common of the two is a hydrous sodium, calcium and aluminium silicate, NaCa2Al5Si5O20·6H2O. Strontium can substitute for the calcium and the appropriate species name depends on the dominant element. The species are visually indistinguishable and the series name thomsonite is used whenever testing has not been performed. Globally, thomsonite is one of the rarer zeolites.

Silicate minerals Rock-forming minerals with predominantly silicate anions

Silicate minerals are rock-forming minerals with predominantly silicate anions. They are the largest and most important class of rock-forming minerals and make up approximately 90 percent of the Earth's crust.

Mineral Element or chemical compound that is normally crystalline and that has been formed as a result of geological processes

A mineral is, broadly speaking, a solid chemical compound that occurs naturally in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are usually excluded, but some minerals are often biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings often syntesize inorganic minerals that also occur in rocks.

Zeolite Microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts

Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that rapidly heating the material, believed to have been stilbite, produced large amounts of steam from water that had been adsorbed by the material. Based on this, he called the material zeolite, from the Greek ζέω (zéō), meaning "to boil" and λίθος (líthos), meaning "stone". The classic reference for the field has been Breck's book Zeolite Molecular Sieves: Structure, Chemistry, And Use.

Thomsonite was first identified in material from Scotland in 1820. It is named for the Scottish chemist Thomas Thomson. The crystal system of thomsonite is orthorhombic. The Mohs hardness is 5 to 5.5. It is transparent to translucent and has a density of 2.3 to 2.4. It may be colorless, white, beige, or somewhat green, yellow, or red. The crystals tend to be long thin blades that typically form radial aggregates, and sometimes fans and tufts. The aggregates are variable and may be spikey in appearance, dense and ball-like, or form worm-like growths. Tight acicular radiating clusters and sphericules are common forms.

Scotland country in Northwest Europe, part of the United Kingdom

Scotland is a country that is part of the United Kingdom. Sharing a border with England to the southeast, Scotland is otherwise surrounded by the Atlantic Ocean to the north and west, by the North Sea to the northeast and by the Irish Sea to the south. In addition to the mainland, situated on the northern third of the island of Great Britain, Scotland has over 790 islands, including the Northern Isles and the Hebrides.

Thomas Thomson (chemist) Scottish chemist

Thomas Thomson was a Scottish chemist and mineralogist whose writings contributed to the early spread of Dalton's atomic theory. His scientific accomplishments include the invention of the saccharometer and he gave silicon its current name. He served as president of the Philosophical Society of Glasgow.

Mohs scale of mineral hardness qualitative ordinal scale characterizing scratch resistance of various minerals

The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German Geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, some of which are more quantitative. The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. 77 AD. While greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting.

Thomsonite occurs with other zeolites in the amygdaloidal cavities of basaltic volcanic rocks, and occasionally in granitic pegmatites. Examples have been found in Faroe Islands (var. Faroelite [1] ), Scotland, Arkansas, Colorado, Michigan, Minnesota, New Jersey, Oregon, Ontario, Nova Scotia, India, and Russia. [2]


Amygdules or amygdales form when the gas bubbles or vesicles in volcanic lava are infilled with a secondary mineral such as calcite, quartz, chlorite or one of the zeolites. Amygdules usually form after the rock has been emplaced, and are often associated with low-temperature alteration. Amygdules may often be concentrically zoned. Rocks containing amygdules can be described as amygdaloidal.

Basalt A magnesium- and iron-rich extrusive igneous rock

Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows.

Volcanic rock rocks composing or associated with volcanoes, volcanic activity or volcanism

Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "volcaniclastics," and these are technically sedimentary rocks.

Nodules of massive thomsonite that display an attractive banded coloring are found along the shore of Lake Superior. Most of these thomsonite nodules and their derived pebbles are less than 0.6 cm (1/4 inch). Those enclosed in basalt are extremely difficult to remove without breaking them. Consequently, a very large percentage of those used as gemstones are from pebbles collected from beaches.

Nodule (geology) Small mass of a mineral with a contrasting composition to the enclosing sediment or rock

In sedimentology and geology, a nodule is small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition, such as a pyrite nodule in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale, from the enclosing sediment or sedimentary rock. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.

Lake Superior largest of the Great Lakes of North America

Lake Superior, the largest of the Great Lakes of North America, is also the world's largest freshwater lake by surface area, and the third largest freshwater lake by volume. The lake is shared by the Canadian province of Ontario to the north, the U.S. state of Minnesota to the west, and Wisconsin and the Upper Peninsula of Michigan to the south. The farthest north and west of the Great Lakes chain, Superior has the highest elevation of all five great lakes and drains into the St. Mary's River.

Related Research Articles

Prehnite transitional ino-phyllosilicate mineral

Prehnite is an inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most often forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well-individualized crystals showing a square-like cross-section, including those found at the Jeffrey Mine in Asbestos, Quebec, Canada. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to yellow, but also colorless, blue, pink or white. In April 2000, rare orange prehnite was discovered in the Kalahari Manganese Fields, South Africa. Prehnite is mostly translucent, and rarely transparent.

Pyroxene single chain inosilicates

The pyroxenes (commonly abbreviated to Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula XY(Si,Al)2O6 where X represents calcium, sodium, iron (II) or magnesium and more rarely zinc, manganese or lithium and Y represents ions of smaller size, such as chromium, aluminium, iron (III), magnesium, cobalt, manganese, scandium, titanium, vanadium or even iron (II). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a common structure consisting of single chains of silica tetrahedra. Pyroxenes that crystallize in the monoclinic system are known as clinopyroxenes and those that cystallize in the orthorhombic system are known as orthopyroxenes.

Stilbite stilbite series, zeolite

Stilbite is the name of a series of tectosilicate minerals of the zeolite group. Prior to 1997, stilbite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named:

Natrolite zeolite mineral

Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10 · 2H2O. The type locality is Hohentwiel, Hegau, Germany.

Scolecite zeolite mineral

Scolecite is a tectosilicate mineral belonging to the zeolite group; it is a hydrated calcium silicate, CaAl2Si3O10·3H2O. Only minor amounts of sodium and traces of potassium substitute for calcium. There is an absence of barium, strontium, iron and magnesium. Scolecite is isostructural (having the same structure) with the sodium-calcium zeolite mesolite and the sodium zeolite natrolite, but it does not form a continuous chemical series with either of them. It was described in 1813, and named from the Greek word, σκώληξ (sko-lecks) = "worm" because of its reaction to the blowpipe flame.

Heulandite heulandite series, zeolite

Heulandite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, heulandite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named:

Mordenite zeolite mineral

Mordenite is a zeolite mineral with the chemical formula, (Ca, Na2, K2)Al2Si10O24·7H2O. According to Ullmann's Encyclopedia of Industrial Chemistry (2005), it is one of the six most abundant zeolites and is used commercially.

Laumontite zeolite mineral

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.

Cavansite phyllosilicate mineral

Cavansite, whose name is derived from its chemical composition, calcium vanadium silicate, is a deep blue hydrous calcium vanadium phyllosilicate mineral, occurring as a secondary mineral in basaltic and andesitic rocks along with a variety of zeolite minerals. Discovered in 1967 in Malheur County, Oregon, cavansite is a relatively rare mineral. It is polymorphic with the even rarer mineral, pentagonite. It is most frequently found in Pune, India and in the Deccan Traps, a large igneous province.

Phillipsite phillipsite series, zeolite

Phillipsite is a mineral series of the zeolite group; a hydrated potassium, calcium and aluminium silicate, approximating to (Ca,Na2,K2)3Al6Si10O32·12H2O. The members of the series are phillipsite-K, phillipsite-Na and phillipsite-Ca. The crystals are monoclinic, but only complex cruciform twins are known, these being exactly like twins of harmotome which also forms a series with phillipsite-Ca. Crystals of phillipsite are, however, usually smaller and more transparent and glassy than those of harmotome. Spherical groups with a radially fibrous structure and bristled with crystals on the surface are not uncommon. The Mohs hardness is 4.5, and the specific gravity is 2.2. The species was established by Armand Lévy in 1825 and named after William Phillips. French authors use the name Christianite (after Christian VIII of Denmark), given by A. Des Cloizeaux in 1847.

Mesolite zeolite mineral

Mesolite is a tectosilicate mineral with formula Na2Ca2(Al2Si3O10)3·8H2O. It is a member of the zeolite group and is closely related to natrolite which it also resembles in appearance.

Brewsterite brewsterite series, zeolite

Brewsterite is the name of a series of tectosilicate minerals of the zeolite group. Prior to 1997, brewsterite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named brewsterite-Sr and brewsterite-Ba. Brewsterite-Sr, the more common of these, is a hydrous strontium and aluminium silicate, (Sr,Ba)2Al4Si12O32·10H2O. Small amounts of barium is usually present replacing part of the strontium. The appropriate species name depends on the dominant element. The species are visually indistinguishable, and the series name brewsterite is still used whenever testing has not been performed.

Belite is an industrial mineral important in Portland cement manufacture. Its main constituent is dicalcium silicate, Ca2SiO4, sometimes formulated as 2 CaO · SiO2 (C2S in cement chemist notation).

Thaumasite sulfate mineral

Thaumasite is a silicate mineral with chemical formula Ca3Si(OH)6(CO3)(SO4)·12H2O. It occurs as colorless to white prismatic hexagonal crystals, typically as acicular radiating groups. It also occurs as fibrous masses. Its Mohs hardness is 3.5 and it has a specific gravity of 1.88 to 1.90. Optically it is uniaxial negative with indices of refraction of nω = 1.507 and nε = 1.468.

Lévyne levyne series, zeolite

Levyne or levynite is a zeolite mineral, i.e. a hydrated silicate mineral. There are two forms of levyne:

Partheite or parthéite is a calcium aluminium silicate and a member of the zeolite group of minerals, a group of silicates with large open channels throughout the crystal structure, which allow passage of liquids and gasses through the mineral. It was first discovered in 1979 in rodingitic dikes in an ophiolite zone of the Taurus Mountains in southwest Turkey. The second discovery occurred in gabbro-pegmatites in the Ural Mountains, Russia. Since its discovery and naming, the chemical formula for partheite has been revised from CaAl2Si2O8•2H2O to include not only water but hydroxyl groups as well. The framework of the mineral is interrupted due to these hydroxyl groups attaching themselves to aluminum centered oxygen tetrahedra. This type of interrupted framework is known in only one other zeolite, the mineral roggianite. As a silicate based mineral with the properties of a zeolite, partheite was first described as zeolite-like in 1984 and listed as a zeolite in 1985. Partheite and lawsonite are polymorphs. Associated minerals include prehnite, thomsonite, augite, chlorite and tremolite.

Okenite phyllosilicate mineral

Okenite (CaSi2O5·2H2O) is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white "cotton ball" formations within basalt geodes. These formations are clusters of straight, radiating, fibrous crystals that are both bendable and fragile.

Gyrolite phyllosilicate mineral

Gyrolite, NaCa16(Si23Al)O60(OH)8·14H2O, is a rare silicate mineral (basic sodium calcium silicate hydrate: N-C-S-H, in cement chemist notation) belonging to the class of phyllosilicates. Gyrolite is also often associated with zeolites. It is most commonly found as spherical or radial formations in hydrothermally altered basalt and basaltic tuffs. These formations can be glassy, dull or fibrous in appearance.