Paulingite

Last updated
Paulingite
General
Category Zeolite Group
Formula
(repeating unit)
(K,Na,Ca)
3–4
(Si,Al)
21
O
42
•17-22H
2
O
IMA symbol Pau [1]
Strunz classification 9.GC.35
Crystal system Cubic
Crystal class Hexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space group Im3m
Identification
ColorColorless, light yellow, orange, red
Crystal habit Typically as euhedral crystals
Cleavage None
Fracture Conchoidal
Mohs scale hardness5
Luster Vitreous to adamantine
Diaphaneity Transparent
Specific gravity 2.085 – 2.24
Refractive index n = 1.472–1.484
Ultraviolet fluorescence None
References [2] [3] [4] [5]

Paulingite or paulingite-K is a rare zeolite mineral that is found in vesicles in the basaltic rocks from the Columbia River near Rock Island Dam, Washington.

Contents

Paulingite was named for Linus Carl Pauling (1901–1994), professor of chemistry, California Institute of Technology and accepted by the International Mineralogical Association in 1960. [4]

The early formation in the crystallization sequence and the high water content suggest that paulingite forms from relatively dilute pore fluids. They have a large unit cell of 3.51 nanometers and an isometric crystal system. This is the largest known inorganic unit cell apart from protein structures.[ citation needed ] Paulingite's characteristic structure can be observed while the remaining water content decomposes. A single crystal X-ray refinement of this chemically different sample material derived three main cation positions, which are inside a so-called paulingite or calcium (Ca), between 8-rings of neighbouring barium (Ba), and in the centre of the non-planar 8-rings of the -cage potassium (K).

Introduction

Kamb and Oke in 1960 first described paulingite from vesicles in the Tertiary, augite-bearing, basaltic rocks at the Rock Island dam in Washington, where it is associated with clinoptilolite (Na,K,Ca)
2–3
Al
3
(Al,Si)
2
Si
13
O
36
·12H
2
O)
, phillipsite (Ca,Na2,K2)3Al6Si10O32·12H2O, calcite (CaCO3), and pyrite (FeS2). Zeolite minerals are crystalline, hydrated aluminosilicate of alkali and alkaline cations with a three-dimensional structure. It is a special group of minerals that is important due to its members' uses in different industries. Due to its special properties like attractive adsorption, cation-exchange, dehydration-rehydration and catalysis properties they are used in the nuclear industry, construction industry, agricultural industry, medical industry, petrochemical industry, space industry and domestic products industry (Fredrick A. Mumpton, 1998). It is a rare zeolite mineral with a dodecahedron crystal form {110} and has a very large unit cell with a = 3.51 nanometers. The mineral information was described by Kamb and Oke (1960) which has Si/Al ratio of 3.0, a BaO range of 0.5–4.1% and 18.5% of water content (Tscherinch and Wise, 1982).

Physical, crystallographic information and structure

A rhombic dodecahedron has twelve faces, each of which is a rhombus. Rhombicdodecahedron.jpg
A rhombic dodecahedron has twelve faces, each of which is a rhombus.

Paulingite is a perfect clear rhombic dodecahedron of 0.1 to 1.0 mm in diameter. Their attachment to vesicles causes a hemispherical shape exhibiting 5 to 6 planes of dodecahedral planes. In the vesicular walls, they appear to be dark brown to black. They are actually clear and colorless due to clarity and their attachment to the vesicular wall. The crystal faces are smooth and planar and have a bright vitreous luster. The crystals have no cleavage. Under a binocular microscope, it resembles chips of ice. Lamellae seen optically may indicate twinning. They have a conchoidal fracture. It has a white streak. Rhombic dodecahedron is the dominant crystal form for paulingite. The hardness of paulingite is 5. The size of the paulingite unit cell is outstanding because it is the largest inorganic compounds exceeding most complex, intermetallic compounds. The measured density is 2.085 g/cm3 and calculated density is 2.10 g/cm3. The figure below shows the dodecahedron shape of paulingite mineral.

Viewing under a petrographic microscope, the crystals contains a scattering of minute bubble-like inclusions. Paulingite is mostly isotropic and in extreme cases that faint, isolated, fuzzy and weak birefringent twinning which is a determining factor for differentiating paulingite from analcite (NaAlSi2O6·H2O). The refractive index at 230 in sodium vapor light by immersion method is 1.473. Single crystal diffraction study provides information that paulingite is cubic and the cubic length of a0 = 35.10 Å. It was determined from rotation photograph using copper Ka radiation, nickel filtered, with the film in self-calibrating arrangement. The reflections were indexed with the help of a zero-layer Weissenberg photograph. Reflections of the type hkl for l = 0 to l = 12 have been examined with equi-inclination weissenberg photographs, and only reflections having h+k+l even are observed, indicating a body-centered lattice. The crystal system is isometric. The space group of the paulingite is Im3m and the point group is 4/m3 2/m (Kamb and Oke 1960).

Geologic occurrence

Paulingite is usually found in vesicles of basalt flows. Because of its rarity, certain chemical factors have to be considered for its formation. The exchangeable cations do not control the formation of paulingite because variations of localities have different percentages to elements; e.g. Riggins zeolites are K rich while Chase Creek is Barium rich. The Si/Al ratio does not control the formation because the ratio is controlled by the pH of the solution. They may have formed around hydrated or partially hydrated alkali and alkaline earth cations which act as a template. Relatively low-saline solutions promote paulingite framework. So it occurs in sub-alkaline rocks. There are following localities where paulingite are also found which include Riggins in Idaho country, Ritter in Grant county and Chase creek in British Columbia. In Europe, Paulingite was found among zeolites of the Giants Causeway in Ireland and two zeolite localities near Howeneeg and Vogelsberg (Tscherinch and Wise, 1982).

Distribution

In the US, at Rock Island Dam, on the Columbia River, Wenatchee, Douglas Co., Washington; from near Riggins, Idaho Co., Idaho; and at Three Mile Creek, near Ritter, Grant Co., Oregon. On Chase Creek, at the junction with Charcoal Creek, north of Falkland, British Columbia, Canada. Large crystals from the Giant's Causeway and Craigahulliar, Portrush, Co. Antrim, Northern Ireland. At Kladno and Vinarice, Czech Republic. In the Höwenegg quarry, Hegau, Baden-Württemberg, and in the Ortenberg quarry, Vogelsberg, Hesse, Germany.

Association

Zeolite mineral species, pyrite and calcite are the important minerals are usually found in association with paulingite.

Related Research Articles

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Zeolite is a family of several microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula Mn+
1/n
(AlO
2
)
(SiO
2
)
x
・yH
2
O
where Mn+
1/n
is either a metal ion or H+. These positive ions can be exchanged for others in a contacting electrolyte solution. H+
exchanged zeolites are particularly useful as solid acid catalysts.

<span class="mw-page-title-main">Stilbite</span>

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:

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Chabazite is a tectosilicate mineral of the zeolite group, closely related to gmelinite, with the chemical formula (Ca,K
2
,Na
2
,Mg)Al
2
Si
4
O
12
•6H
2
O
. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.

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<span class="mw-page-title-main">Scolecite</span>

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.

<span class="mw-page-title-main">Heulandite</span>

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<span class="mw-page-title-main">Celadonite</span>

Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminium and hydroxide with formula K(Mg,Fe2+
)(Fe3+
,Al)[Si
4
O
10
](OH)
2
.

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Clinoptilolite is a natural zeolite composed of a microporous arrangement of silica and alumina tetrahedra. It has the complex formula (Na,K,Ca)
2–3
Al
3
(Al,Si)
2
Si
13
O
36
•12H
2
O
. It forms as white, green to reddish tabular monoclinic tectosilicate crystals with a Mohs hardness of 3.5 to 4 and a specific gravity of 2.1 to 2.2. It commonly occurs as a devitrification product of volcanic glass shards in tuff and as vesicle fillings in basalts, andesites and rhyolites. It was described in 1969 from an occurrence in the Barstow Formation, San Bernardino County, California. Sodium levels in clinoptilolite are generally higher than potassium levels, as is the case with the San Bernardino Barstow Formation, but there are sources that are potassium-rich and have minimal sodium.

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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.

Zeolites are found in several locations in southern and central Idaho.

<span class="mw-page-title-main">Tacharanite</span> Calcium aluminium silicate hydrate mineral

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References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. Mineralienatlas
  3. http://rruff.geo.arizona.edu/doclib/hom/paulingitek.pdf Mineral Handbook
  4. 1 2 http://webmineral.com/data/Paulingite-K.shtml Webmineral
  5. http://www.mindat.org/min-7219.html Mindat