Soddyit

Soddyit
	Soddyite crystals, 1 mm in size, from the Swambo Mine , Katanga Province , Democratic Republic of the Congo
General and classification
chemical formula	(UO 2 ) 2 (SiO 4 ) · 2H 2 O
Mineral class; (and possibly department)	Silicates and Germanates
System no. to Strunz ; and to Dana	9.AK.05 ( 8th edition : VIII / B.36) ; 53.03.03.01
Crystallographic Data
Crystal system	orthorhombic
Crystal class ; symbol	orthorhombic-dipyramidal
Room group (no.)	Fddd (No. 70)
Lattice parameters	a = 8.32 Å ; b = 11.21 Å; c = 18.71 Å Please complete the source as an individual reference
Formula units	Z = 8 Please complete the source as an individual reference
Physical Properties
Mohs hardness	3 to 4
Density (g / cm 3 )	4,627
Cleavage	completely after {001}, clearly after {111}
Break ; Tenacity	uneven
colour	yellow, canary yellow, yellow green
Line color	yellow
transparency	translucent
shine	Glass gloss, fat gloss
radioactivity	very strong
Crystal optics
Refractive indices	n α = 1.650 to 1.654 ; n β = 1.685 ; n γ = 1.699 to 1.715
Birefringence	δ = 0.049 to 0.061
Optical character	biaxial negative
Pleochroism	weak: X = colorless; Y = pale green; Z = yellow green

The mineral soddyite is a rather seldom occurring uranium mineral from the mineral class of "silicates and germanates" with the chemical composition (UO ₂ ) ₂ (SiO ₄ ) · 2H ₂ O. It crystallizes in the orthorhombic crystal system and develops both prismatic and pyramidal yellow crystals .

Etymology and history

Soddyit was first described by Alfred Schoep in 1922 . On a step of orange-brown Curit crystals from the Kasolo Mine in Katanga (today: Democratic Republic of the Congo ), he found another yellow mineral, for which he proposed the name "Soddite", in honor of the chemist Frederick Soddy , who in 1921 Nobel Prize for his work on radioactive materials and the nature of isotopes. Billiet changed this name to "Soddyit" in 1926, which was also accepted by Schoep and eventually used in all of his other publications.

The type mineral is in the Natural History Museum in Paris .

classification

The outdated 8th edition of the Strunz lists the sodyite among the "island silicates with non-tetrahedral anions" with the system no. VIII / B.36 and the only other member Swamboit- (Nd) .

The 9th, completely revised edition of Strunz lists the soddyite in the section K " Uranyl island and polysilicates with a uranium: silicon ratio of U: Si = 2: 1 " in the group 9.AK.05 , whereby soddyite is the is the only representative of this group.

The systematics of minerals according to Dana , which is common in the English-speaking world , assigns soddyite to the group "Other uranyl silicates" of the island silicates department, but there in the department of " Island silicates with SiO ₄ groups and other anions and complex cations with (UO ₂ ) " with the system no. 53.03.03.01 a.

Crystal structure

Soddyite crystallizes in the orthorhombic space group Fddd with the lattice parameters a = 8.32 Å ; b = 11.21 Å; c = 18.71 Å and 8 formula units per unit cell . Soddyite is the only known uranyl mineral that has a uranium-silicon ratio of 2: 1. In the crystal structure, a tetrahedral silicate anion links six pentagonal-bipyramidal uranyl ions. The uranyl polyhedra are linked by edges. The fifth equatorial coordination point is occupied by a water molecule, the hydrogen atoms of which form hydrogen bonds to the uranyl oxygen atoms. This connection scheme creates a three-dimensional network.

Three-dimensional packing structure of sodyite in the direction of the crystallographic a -axis
Three-dimensional packing structure of sodyite in the direction of the crystallographic c -axis
3D animation of the packaging structure
Coordination of the silicon atom __ U __ O __ Si __ H

properties

The mineral is very radioactive due to its uranium content of 71.25% . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the Folgezerfälle of the natural decay chains a specific activity of about 127.5 K for the mineral Bq stated / g (compared to natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and the composition of the levels; selective enrichment or depletion of the radioactive decay products is also possible and changes the activity.

Education and Locations

Paragenesis of sodyite (yellow) with rutherfordin (brown) from the Kolwezi mine , Democratic Republic of the Congo

Paragenesis of Soddyit (yellow) with Swamboit- (Nd) (pale yellow) from the Swambo Mine , Democratic Republic of the Congo

Paragenesis of sodyite (yellow) and curite (orange) on heterogenite (black) from the Kasolo mine , Democratic Republic of the Congo

Soddyite forms as a secondary uranium mineral in the oxidation zone of primary uranium ores. It is found as a silicate mineral together with the other uranyl silicates kasolite , sclodovskite and uranophane . Furthermore, it is found in the classic association with the basic lead-uranyl oxide curite , as well as with the copper-uranyl phosphate torbernite . In addition to the type locality in Shinkolobwe ( Kasolo Mine ), the Musonoi Mine and the Swambo Mine in the Democratic Republic of the Congo are also found . In Germany it is known from the Krunkelbach mine in Menzenschwand and from Johanngeorgenstadt and Tirpersdorf in Saxony . Furthermore, it could be found in the Radium Ridge in Australia , in Lodève in France , in Capoterra in Italy , in Eger and Karlsbad in the Czech Republic , on Lake George in Canada , in Peña Blanca in Mexico , in Ust'-Uyuk in Russia , as well as in Nevada and Wyoming in the USA .

Precautions

Due to the strong radioactivity of the mineral, mineral samples from soddyite should only be kept in dust- and radiation-proof containers, but above all never in living rooms, bedrooms or workrooms. Likewise, because of the high toxicity and radioactivity of uranyl compounds, absorption into the body ( incorporation , ingestion ) should be prevented in any case and, for safety, direct body contact should be avoided and face masks and gloves should be worn when handling the mineral.

literature

Soddyite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 71.4 kB )

Web links

Commons : Soddyit - collection of pictures, videos and audio files

Individual evidence

↑ ^a ^b ^c ^d ^e ^f Soddyite at Webmineral.com
↑ ^a ^b Mindat - Soddyite
↑ A. Schoep, La soddite, nouveau minéral radioactif In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences 1922, 174, pp. 1066-1067. ( PDF, 107 kB (French) )
^ ET Wherry, EF Holden, New minerals - new species In: American Mineralogist 1922, 7, pp. 178-180. ( PDF, 197 kB (English))
^ DH Gorman, Studies of radioactive compounds: V - soddyite In: American Mineralogist 1952, 37, pp. 386-393 ( PDF, 512 kB (English))
↑ FV Stohl, DK Smith, The crystal chemistry of the uranyl silicate minerals In: American Mineralogist 1981, 66, pp. 610–625 ( PDF 1.6 MB (English))

[Webmineral-1] ↑ ^a ^b ^c ^d ^e ^f Soddyite at Webmineral.com

[Mindat-2] Mindat - Soddyite

[Schoep-3] A. Schoep, La soddite, nouveau minéral radioactif In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences 1922, 174, pp. 1066-1067. ( PDF, 107 kB (French) )

[Holden-4] ET Wherry, EF Holden, New minerals - new species In: American Mineralogist 1922, 7, pp. 178-180. ( PDF, 197 kB (English))

[Gorman-5] DH Gorman, Studies of radioactive compounds: V - soddyite In: American Mineralogist 1952, 37, pp. 386-393 ( PDF, 512 kB (English))

[Stohl-6] FV Stohl, DK Smith, The crystal chemistry of the uranyl silicate minerals In: American Mineralogist 1981, 66, pp. 610–625 ( PDF 1.6 MB (English))