Uranophane

• Uranotil
• Modification: uranophane -alpha
• Modification: uranophane -beta

Canary- yellow

The mineral uranophane (also Uranotil ) is a common island of uranium silicate with the chemical composition Ca [ UO2 | SiO3OH ] 2 • 5H2O. It crystallizes in the monoclinic crystal system and usually develops needle-like crystals to about 1 cm in size and radial-, but also granular to massive mineral aggregates or crusty coatings from yellow to brown in color. Uranophane is known to crystallize in two different space groups as uranophane -alpha or beta - uranophane. Both modifications are manifested in a different crystal habit, which, however, is often difficult to distinguish for the layman and allowed only upon closer examination under the microscope an assignment.

Special Features

Uranophane is considered very highly radioactive due to its uranium content of up to 40.6 %. Taking into account the proportions of radioactive elements in the idealized empirical formula and the Folgezerfälle the natural decay series a specific activity of 72.5 kBq / g for the specified mineral (compared to natural potassium 0.0312 kBq / g). The quoted value can vary significantly depending on the mineral content and composition of the stages are also selective on or depletions of radioactive decay products possible and changing the activity.

Occasionally, Uranophan show under UV light, a weak green fluorescence. Typically, the mineral is, however, non- fluorescent.

Uranophan can be easily decomposed by acids.

Etymology and history

Was first found Uranophan 1853 at Copper Mountain ( Tarnów ) in Upper Silesia (Poland) and described by Martin Websky, of the mineral after its uranium content and the Greek word φαίνω [ pronounced " phanos " ] for seem or appear so put together " such as uranium appear " named.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Uranophan belonged to the general ward of the " island silicates with tetrahedral anions foreign ", where he was named. , The " Uranophangruppe " with the system no Formed VIII/B.34 and the other members Boltwoodite, cuprosklodowskite, Kasolit, Natroboltwoodit, Oursinit, Sklodowskit and uranophane - beta.

Since the full review of the Strunz'schen Mineral classification in the 9th edition (2001), this department is divided precisely by the absence or presence of other anions, the structure or the molar ratio of uranium to silicon. The uranophane is accordingly in the department of " uranyl island and layer silicates with the molar ratio U: = 2 Si: 1" to find out where he, together with Boltwoodite, Kasolit, Natroboltwoodit and uranophane - beta, the unnamed group 9.AK.15.

The commonly used in English-speaking classification of minerals according to Dana assigns the Uranophan also in the Department of island silicates, there, however, in the department of " island silicates with SiO4 groups and other anions and complex cations with ( UO2) " where he as the eponymous mineral " Uranophangruppe " with the system number. 53.03.01 forms.

Modifications and varieties

Uranophane -alpha is dimorphic with uranophane -beta, which also crystallizes in the monoclinic crystal system, but in a different space group (see also structural data ).

Education and Locations

Uranophane is one of the most common Uransilicaten. As a typical secondary mineral it forms in uranium deposits and pegmatites by weathering of uraninite. Accompanying minerals are next uranophane - beta, you still Kasolit, autunite and meta- autunite, Phosphuranylite, Torbernite and various uranium oxides, but also calcite, malachite, almandine and muscovite.

Worldwide, Uranophan so far (as of 2010) are detected in more than 700 localities, so among other things in Egypt, Algeria, Argentina, Australia, Brazil, China, Finland, Germany, France, India, Italy, Japan, Kazakhstan, Democratic Republic of Congo, Madagascar, Mexico, Namibia, Norway, Austria, Poland, Portugal, Romania, Russia, Sweden, Switzerland, Slovakia, Spain, South Africa, Tajikistan, Tanzania, Czech Republic, Hungary, Uzbekistan, the United Kingdom ( UK) and in the United States of America (USA).

Are worth mentioning especially the localities " Musonoi Mine" at Kolwezi and " Shinkolobwe Mine ( Kasolo mine ) " at Shinkolobwe in the Congolese province of Katanga, where crystals were found to about 1 cm in size. Beautiful, radiating aggregates were from the " Madawaska Mine ( Faraday Mine) " in Bancroft in Hastings County ( Canada ) to be recovered.

Use

Uranophane is used as uranium ore.

Crystal structure

Uranophane -alpha crystallizes in the monoclinic space group P21 ( Raumgruppen-Nr. 4) with the lattice parameters a = 15.91 Å; b = 7.00 Å; c = 6.67 Å and 97.3 ° β = and 2 formula units per unit cell.

Uranophane -beta (or β - uranophane ) crystallizes also monoclinic, but in the space group P21 / a with lattice parameters a = 13.97 Å; b = 15.44 Å; c = 6.63 Å and 91.4 ° β = 4 and formula units per unit cell.

The figures below illustrate the different crystal lattice of the two Uranophan modifications.

Packing picture of uranophane -alpha in the direction of the crystallographic a- axis ( __ U __ O __ Ca Si __ __ water molecules)

Unit cell of uranophane -beta in the direction of the crystallographic a- axis ( __ U __ O __ Ca Si __ __ water molecules)

Packing picture of uranophane -beta in the direction of the crystallographic c- axis ( __ U __ O __ Ca Si __ __ water molecules)

Precautions

When dealing with the radioactive Uranophan is to ensure adequate radiation protection. To prevent incorporation ( uptake into the body ), is thorough hand washing after handling with bare hands is recommended.