Gaylussite

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Gaylussite
Gaylussite-304155.jpg
Gaylussite crystal from Lake Amboseli , Amboseli National Park , Kenya (size: 3.1 × 1.5 × 1.4 cm)
General and classification
chemical formula Na 2 Ca [CO 3 ] 2 • 5 H 2 O
Mineral class
(and possibly department) 		Carbonates
System no. to Strunz
and to Dana 		5.CB.35 ( 8th edition : V / D.02)
02.15.02.01
Similar minerals Natrite , Thermonatrite , Pirssonite , Trona
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) C 2 / c (No. 15)
Lattice parameters a  = 14.361  Å ; b  = 7.781 Å; c  = 11.209 Å
β  = 127.84 °
Formula units Z  = 4
Frequent crystal faces {110}, {011}, {011}
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) 2
Cleavage perfectly
Break ; Tenacity shell-like, very brittle
colour colorless, white, gray, yellowish
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.444
n β  = 1.516
n γ  = 1.523
Birefringence δ = 0.079
Optical character biaxial negative
Axis angle 2V = 34 °
Other properties
Chemical behavior readily soluble in dilute. acids to CO 2 -Abgabe

Gaylussite is a rarely occurring mineral from the mineral class of carbonates (and nitrates) [*] . It crystallizes in the monoclinic crystal system with the chemical composition Na 2 Ca [CO 3 ] 2  • 5 H 2 O.

In nature, gaylussite occurs mostly in the form of tabular to prismatic or dipyramidal crystals that are either colorless or white, gray and yellow in color.

Special properties

Gaylussite melts in front of the soldering tube , and when dissolved in water, Na 2 CO 3 splits off.

Etymology and history

Gaylussite was first found in 1826 near Lagunillas / Mérida in Venezuela and described by Jean-Baptiste Boussingault (1802-1887), who named the mineral after the French chemist and physicist Joseph Louis Gay-Lussac (1778-1850), who was known for his gas laws .

classification

In the now outdated 8th edition of the systematics of minerals according to Strunz , gaylussite still belongs to the common mineral class of "carbonates, nitrates and borates" and there to the department of "hydrous carbonates without foreign anions ", where it is combined with baylissite , chalconatronite , pirssonite , Soda , Thermonatrite and Trona form a separate group.

After extensive revisions of the Strunz'schen mineral systematics, among other things, the borates were spun off in the 9th edition and now form a class of their own. However, gaylussite is still assigned to the “water-containing carbonates without foreign anions”, which, however, are more precisely divided according to the type and size of the cations involved . The mineral is therefore in the sub-section " With large cations (alkali and alkaline earth carbonates) ".

The systematics of minerals according to Dana , which is common in the English-speaking world , assigns gaylussite, like the 8th edition of Strunz's systematics, to the common class of “carbonates, nitrates and borates” and there to the division of “ hydrous carbonates with the general formula A + m B 2+ n (XO 3 ) p  • x (H 2 O) and the general molar ratio (m + n): p> 1: 1 "

Modifications and varieties

As Thinolith one is Pseudomorphose of calcite after Gaylussite referred.

Education and Locations

Gaylussite from the type locality Lagunillas, Venezuela. Exhibited in the Mineralogical Museum Bonn

Gaylussite is mainly formed by sedimentation in evaporites , but also in slate sediments of alkali lakes and is found there in paragenesis with various minerals such as aegirine , northupite , pectolite , pirssonite , shortite , thermonatrite , trona and villiaumite .

So far, Gaylussite has been found at almost 40 sites (status: 2009), so in addition to its type locality Lagunillas in Venezuela, among others, at Laguna Santa Maria ( Salta ) in Argentina; on Lake Chad in West Africa; at Chabyêr Caka (Zabuye Salt Lake) in Tibet; in the "Wadi el Natrun" in the Sketian desert (Sahara, Africa); in Italian Tuscany ; at the alkaline “Amboseli Lake” in the Kenyan Amboseli National Park ; at Chicxulub Crater in Mexico; in the Mongolian Gobi desert ; on the Kola Peninsula in Russia; near Dolný Harmanec ( Niederhermanetz ) in Slovakia; in the "salt pan crater" near Pretoria in South Africa; in the salt mine near Bex in Switzerland and in the US regions of California , Nevada , Oregon , Washington and Wyoming .

Crystal structure

Gaylussite crystallizes monoclinically in the space group C 2 / c with the lattice parameters a  = 14.361  Å ; b  = 7.781 Å; c  = 11.209 Å and β = 127.84 ° as well as four formula units per unit cell .

See also

literature

Web links

Commons : Gaylussite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c American Mineralogist Crystal Structure Database - Gaylussite (English)
  2. ↑ a b c Mindat - Gaylussite (English)
  3. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp.  582 (first edition: 1891).
  4. ↑ Mindat - Localities for Gaylussite