Decorative, but a little deadly – Torbernite

 What does it look like?

The crystal structure of Torbernite. Here the atom colours are; blue – uranium, orange – copper, purple - phosphorus, red – oxygen. Image generated by Mercury.

The crystal structure of Torbernite. Here the atom colours are; blue – uranium, orange – copper, purple – phosphorus, red – oxygen. Image generated by Mercury.

What is it?

Torbernite crystals exhibit exceptionally beautiful shades of green, from emerald to grass-green to apple-green, and thus may entice you to collect these crystals as ornaments for your tables – but beware; these crystals are capable of slowly leaking lethal radon gas which can cause lung cancer.

Image of a collection of torbernite crystals. Taken from: http://www.gemstonesadvisor.com/torbernite/

Image of a collection of torbernite crystals. Taken from: http://www.gemstonesadvisor.com/torbernite/

Torbernite crystals, Cu(UO2)2(PO4)2)·12H2O, are formed through a complex reaction of phosphorus, copper, water and uranium and form as secondary uranium deposits in granitic rocks. These materials belong to the autunite group and are found in the alteration zone of hydrothermal veins and pegamites that contain uraninite. Torbernite materials possess a significant environmental interest in that they exert an impact on the mobility of uranium in phosphate bearing systems such as uranium deposits and so can act as a reactive barrier that uses phosphate to limit the transport of uranium in groundwater. As such, the presence of torbernite has been used by prospectors as an indicator of uranium deposits.

Where did the structure come from?

Torbernite occurs in tabular blocks that may be very thin to moderately thick. The crystals have a perfect cleavage parallel to the basal plane and thus can resemble mica. This particular structure of torbernite that we have featured was presented in Locock, A.J. and Burns, B.C. The Canadian Mineralogist, 2003, vol. 41, pp. 489 – 502.

Advertisements

A powering mineral – Uraninite

What does it look like?

The light blue elements are uranium and the red are oxygen.  Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

The light blue elements are uranium and the red are oxygen. Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

Australia is the world’s third largest producer of Uranium ore, but as a country as a whole it actually holds the largest reserves of this element.  Most uranium lives in the ground as uraninite, which is often known as pitchblende.  Uranite is, in fact uranium oxide UO2, but the mineral can often be more oxidised and have domains of U3O8.

Where did the structure come from?

Uraninite is #9009049 in the crystallography open database.

Another strange element – β Uranium

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

Uranium is a complicated element as it is, but like carbon is can also form in a number of crystals structures – three have been identified to date; known as α, β and γ forms. The α and γ structures were found to be relatively simple, that is with only a few atoms in each repeating unit of the structure. However, that wasn’t the case for β Uranium, it’s a very complicated structure with 30 atoms in the basic unit cell needed to build the whole structure. At the time it was discovered, in 1951, it was thought that this structure was the same as that being discovered in some metal alloys, known as ‘σ-phases’.  Though this was found not to be the case, this structure has still left many puzzling why elements (where the atoms should all be identical) would form such elaborate structures.

Where did the structure come from?

The image of the crystal structure was built from information in the paper by Tucker and Senio in 1953, which was an improvement on their original structure determination.

The crystal structure rainbow – Glowing in UV, Andersonite

Just to extend on our theme for this week a little – how about a crystal structure that glows in UV light?  It’s also one of the minerals in this post we mentioned yesterday, so it ties up things very nicely!

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

Andersonite is a rare Uranium carbonate mineral that was first found in Arizona in the US. It’s fluorescent and will glow a yellowy-green under UV light. As you can see hinted in the picture, it’s crystal structure is quite complex – with units of carbonate (CO3, brown carbon atoms surrounded by red oxygen atoms), sodium (yellow atoms) and calcium (blue) atoms which all surround the uranium (green) atoms. Because of the way uranium are made up, they can bond with up to 6 other atoms at a time. This makes for quite a variety of minerals that it can form.

Where did the structure come from?

The crystal structure of Andersonite was determined in 1981, and it #907645 in the open crystallography database.