Thermonatrite

Thermonatrite
	Villiaumite with a white encrustation of Thermonatrite
General and classification
chemical formula	Na 2 [CO 3 ] • H 2 O
Mineral class; (and possibly department)	Carbonates (and relatives)
System no. to Strunz ; and to Dana	5.CB.05 ( 8th edition : V / D.02) ; 01/15/01/01
Crystallographic Data
Crystal system	orthorhombic
Crystal class ; symbol	rhombic-pyramidal mm 2
Room group (no.)	Pca 2 1 (No. 29)
Lattice parameters	a = 10.72 Å ; b = 5.26 Å; c = 6.47 Å
Formula units	Z = 4
Physical Properties
Mohs hardness	1 to 1.5
Density (g / cm 3 )	measured: 2.255 (synthetic); calculated: 2.262
Cleavage	Please complete
colour	colorless, white, gray-yellow
Line color	White
transparency	transparent to translucent
shine	Glass gloss, matt
Crystal optics
Refractive indices	n α = 1.420 ; n β = 1.506 ; n γ = 1.524
Birefringence	δ = 0.104
Optical character	biaxial negative
Axis angle	2V = measured: 48 °; calculated: 46 °
Other properties
Chemical behavior	water soluble; already soluble in weak acids with elimination of CO 2
Special features	alkaline (lye-like, soapy) taste, readily dehydrated

Thermonatrite is a rarely occurring mineral from the mineral class of the " carbonates ( and relatives )". It crystallizes in the orthorhombic crystal system with the composition Na ₂ [CO ₃ ] • H ₂ O. From a chemical point of view, it is a hydrous sodium carbonate . It is mainly found in the form of white or gray-yellow, powdery crusts and efflorescence. It also very rarely develops colorless to white, needle-like crystals .

Special properties

Since thermonatrite is on the one hand easily soluble in water, but on the other hand also readily dehydrated in the air, i.e. it splits off water of crystallization and dries out, it must be kept protected as a mineral sample in an airtight container.

Etymology and history

Thermonatrite was named in 1845 by Wilhelm Ritter von Haidinger , who named the mineral after the Greek word θερμός [thermós] for warm and the related mineral soda or the chemical compound soda , alluding to its origin as "soda dried out by the addition of heat".

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the thermonatrite belonged to the common mineral class of "carbonates, nitrates and borates " and there to the department of "hydrous carbonates without foreign anions ", where it, together with baylissite , chalconatronite , Gaylussit , Pirssonit , Soda and Trona formed an independent group V / D.02 .

The 9th edition of Strunz's mineral systematics, valid since 2001 and used by the International Mineralogical Association (IMA), assigns thermonatrite to the new class of “carbonates and nitrates” (the borates now form a separate class). There it still belongs to the division of “carbonates without additional anions; with H ₂ O “. However, this section is even more precisely subdivided according to the size of the cations involved , so that the mineral, according to its composition, can be found in the sub-section "With large cations (alkali and alkaline earth carbonates)", where it is the only member of the unnamed group 5 .CB.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns thermonatrite to the common class of "carbonates, nitrates and borates", like the old Strunz'sche systematics, but there it belongs to the category of "hydrous carbonates". Here he is to be found as the only member of the unnamed group 01/15/01 within the subdivision of " Water-containing carbonates with A ⁺ (XO ₃ ) • x (H ₂ O) ".

Education and Locations

Thermonatrite usually forms on the bottoms of salt lake and evaporite - deposits rare, even in volcanic fumaroles and hydrothermal veins related species carbonatites . Accompanying minerals include halite , soda and trona .

In total, Thermonatrite has so far (as of 2011) been detected at around 50 sites. In Austria the mineral was found on the Tyrolean Gratlspitze and in Switzerland it was found in the salt mines near Bex in the canton of Vaud.

Further sites are the Wadi Natrun in Egypt; Canton of San Juan (province of Nor Lípez) and Laguna Kollpa ( province of Sur Lípez ) in Bolivia; Damxung and Inner Mongolia in China; Narsaq in Greenland; Mont Saint-Hilaire ( Montérégie Hill ) in Canada; several places in the Great Hungarian Plain , Szeged and Debrecen in Hungary; of Mount Vesuvius in Italy; the Lake Bogoria and the volcano Suswa in the Rift Valley in Kenya; the Mandara Lake in the Libyan region Fessan ; Antsirabe in Madagascar; Tolbatschik on Kamchatka , several places on the Kola peninsula and Verkhne-Chusovskie Gorodki in the Urals in Russia; of Lake Natron in Tanzania and several salt lakes and salt mines in the US states of California , Michigan , Nevada , New Mexico , Oregon , Utah and Washington .

Synthetic manufacture

Thermonatrite can also be produced artificially with the help of a solution of sodium hydrogen carbonate which is saturated at 25 ° to 37 ° C and which is slowly cooled. If the solution is less saturated and at a lower temperature, however, soda crystals will develop.

Crystal structure

Thermonatrite crystallizes orthorhombically in the space group (space group no. 29) with the lattice parameters a = 10.72 Å ; b = 5.26 Å and c = 6.47 Å and 4 formula units per unit cell . ${\ displaystyle \ Pca2_ {1}}$