Swamboit- (Nd)
| Swamboit- (Nd) | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.AK.20 ( 8th edition : VIII / B.36) 03.03.01.08 |
| Similar minerals | * IMA 1981-008
|
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic, 2 / m |
| Room group (no.) | P 2 1 / a (No. 14) |
| Lattice parameters |
a = 17.64 Å ; b = 21 Å; c = 20.12 Å β = 103.42 ° |
| Formula units | Z = 6 |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | 4.06 |
| Cleavage | good after {201} |
| colour | light yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| radioactivity | very strong |
| Crystal optics | |
| Refractive indices |
n α = 1.640 n β = 1.661 n γ = 1.663 |
| Birefringence | δ = 0.023 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 34 °; calculated: 32 ° |
| Pleochroism | weak: X = colorless; Y = pale yellow; Z = pale yellow |
The mineral Swamboit- (Nd) is a very rarely occurring uranium mineral from the mineral class of "silicates and germanates" with the chemical composition Nd 0.333 [(UO 2 ) (SiO 3 OH)] (H 2 O) ∼2.5 . It crystallizes in the monoclinic crystal system and develops fine, light yellow, needle-like crystals or radial aggregates.
Etymology and history
Swamboit- (Nd) was described for the first time in 1981 by Michel Deliens and Paul Piret as fine light yellow needles with a maximum length of 0.8 mm and a thickness of 0.05 mm in paragenesis with 0.5 cm Soddyite crystals and powdery red curite . They named it after its type locality , the Swambo Mine in Katanga , today's Democratic Republic of the Congo. In February 2017, the chemical formula was redefined and the original name Swamboit was changed to Swamboit- (Nd).
The type mineral is located in the Royal Museum for Central Africa in Tervuren , Belgium .
classification
The outdated 8th edition of Strunz lists the Swamboit- (Nd) among the "island silicates with non-tetrahedral anions" with the system no. VIII / B.36 and the only other member Soddyit .
The 9th, completely revised edition of Strunz lists the Swamboit- (Nd) in the section K " Uranyl island and polysilicates with a uranium: silicon ratio of U: Si = 2: 1 " in group 9.AK.20 , whereby Swamboit- (Nd) is the only representative of this group.
The systematics of minerals according to Dana , which is common in the English-speaking world , assigns the Swamboit (Nd) to the uranophane group of the island silicates department, but there in the department of " island silicates with SiO 4 groups and other anions as well as complex cations with (UO 2 ) " with the system no. 53.03.01.08 a.
Crystal structure
Swamboit- (Nd) crystallizes in the monoclinic space group P 2 1 / a with the lattice parameters a = 17.64 Å ; b = 21 Å; c = 20.12 Å, β = 103.42 and 6 formula units per unit cell .
Due to the lack of a single crystal structure analysis, the sum formula of Swamboit- (Nd) cannot be given with sufficient accuracy. In their work, Deliens and Piret compare swamboite with the other uranyl silicates sclodovskite , cuprosklodovskite , uranophane , kasolite and boltwoodite and suggest that the protons (H) can be present in the crystal in the form of H 3 O + or SiO 3 OH 3− . However, later work by Stohl and Smith on cuprosklodovskite and by Peter Burns on boltwoodite suggest that it is more of a SiO 3 OH 3− group - however, further investigations are still pending. Naturally, no statement is made about the geometry and chemical nature of the U 6+ cation.
properties
The mineral is very radioactive due to its uranium content of 56.3% . Taking into account the proportions of the radioactive elements in the idealized empirical formula and the subsequent decays of the natural decay series, a specific activity of around 100.9 k Bq / g is specified for the mineral (for comparison: 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
Swamboit- (Nd) forms as a secondary uranium mineral in the oxidation zone of primary uranium ores. It is found as a silicate mineral in particular in association with soddyite . The only other known Parageneses are finds of Soddyite with plaster of paris and curite . In addition to its type locality, the Swambo Mine in the Democratic Republic of the Congo , Swamboit- (Nd) has only been found at one other site, the Jomac Mine in the USA.
Precautions
Due to the strong radioactivity of the mineral, mineral samples from Swamboit- (Nd) should only be kept in dust- and radiation-proof containers, but especially never in living rooms, bedrooms or work rooms. 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.
See also
literature
- Swamboite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( PDF 70.6 kB ).
Web links
- Mineral Atlas: Swamboite- (Nd)
- Photos of Swamboit on the website of the Association des Géologues Amateurs de Belgique (AGAB)
Individual evidence
- ↑ a b IMA / CNMNC List of Mineral Names; May 2017 (PDF 1.66 MB)
- ↑ a b c d e Swamboite at Webmineral.com
- ↑ a b c d Mindat - Swamboite- (Nd)
- ↑ a b M. Deliens, P. Piret: La swamboïte, nouveau silicate d'uranium hydraté du Shaba, Zaïre . In: Canadian Mineralogist . 1981, 19, pp. 553-557 ( PDF, 740 kB , French).
- ^ 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).
- ^ RC Burns: The Structure of Boltwoodite and Implications of Solid Solution Toward Sodium Boltwoodite . In: The Canadian Mineralogist . 1998, 36, pp. 1069-1075 ( PDF 569 kB , English).