Tranquillityite

Discovery

In 1970, materials scientists found a new unnamed Fe-Ti-Zr silicate mineral containing rare earths and Y in lunar rock sample 10047. The first detailed analysis of the mineral was published in 1971 and the name "tranquillityite" was proposed and later accepted by the International Mineralogical Association. It was later found in lunar rock samples from all Apollo missions.

Together with armalcolite and pyroxferroite, it is one of the three minerals which were first discovered on the Moon, before terrestrial occurrences were found. Fragments of tranquillityite were later found in Northwest Africa, in the NWA 856 Martian meteorite.

Terrestrial occurrences of tranquillityite were found in six localities in the Pilbara region of Western Australia in 2011. The Australian occurrences include a number of Proterozoic to Cambrian age diabase and gabbro dikes and sills. It occurs as interstitial grains with zirconolite, baddeleyite, and apatite associated with late stage intergrowths of quartz and feldspar.

Properties

Tranquillityite forms thin stripes up to 15 by 65 micrometres in size in basaltic rocks, where it was produced at a late crystallization stage. It is associated with troilite, pyroxferroite, cristobalite and alkali feldspar. The mineral is nearly opaque and appears dark red-brown in thin crystals. Presence of a significant amount of uranium allowed scientists to estimate the age of tranquillityite and some associated minerals in Apollo 11 samples as 3710 million years using the uranium–lead dating technique.

Irradiation by alpha particles generated by uranium decay is believed to be the origin of the predominantly amorphous metamict structure of tranquillityite. Its crystals were obtained by annealing the samples at 800 °C for 30 minutes. Longer annealing did not improve the crystalline quality, and annealing at higher temperatures resulted in spontaneous fracture of samples.

The crystals were initially found to have a hexagonal crystal structure with the lattice parameters, a = 1.169 nm, c = 2.225 nm and three formula units per unit cell, A tranquillityite-like crystalline phase has been synthesized by mixing oxide powders in an appropriate ratio, determined from the chemical analysis of the lunar samples, and annealing the mixture at 1500 °C. This phase was not pure, but intergrown with various intermetallic compounds.

References

;Citations ;Bibliography

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. {{harvnb. Lovering et al.. 1971
3. {{harvnb. Lovering et al.. 1971
4. Lovering et al.. 1971
5. "Tranquillityite". Mindat.org.
6. "Tranquillityite". Webmineral.
7. {{harvnb. Fleischer. 1973
8. [http://rruff.geo.arizona.edu/doclib/hom/tranquillityite.pdf Handbook of Mineralogy]
9. {{harvnb. Ramdohr. El Goresy. 1970
10. {{harvnb. Cameron. 1970
11. {{harvnb. Dence. Douglas. Plant. Traill. 1970
12. Meyer, Charles. (2009). "Sample 10047:Ilmenite Basalt (low K) 138 grams Figure". Nasa.
13. (2009). "The official IMA-CNMNC List of Mineral Names". [[International Mineralogical Association]].
14. {{harvnb. Heiken. Vaniman. French. 1991
15. {{harvnb. Walker. Fleischer. Buford Price. 1975
16. Samples were dated using Pb/Pb ion probe techniques.{{harvtxt. Hinthorne. Andersen. Conrad. Lovering. 1979
17. {{harvtxt. Rasmussen. Fletcher. Muhling. 2008
18. {{harvnb. Hinthorne. Andersen. Conrad. Lovering. 1979
19. [http://curator.jsc.nasa.gov/lunar/letss/Mineralogy.pdf Lunar Sample Mineralogy], NASA
20. {{harvnb. Russell et al.. 2002
21. {{harvnb. Leroux. Cordier. 2006
22. {{harvnb. Rassmussen et al.. 2012
23. The analyzed samples contain less than 10% impurities (Y, Al, Mn, Cr, Nb and other [[rare-earth element]]) and up to 0.01% (100 [[parts per million. ppm]]) of [[uranium]].{{harvnb. Lovering et al.. 1971
24. {{harvnb. Rasmussen. Fletcher. Muhling. 2008
25. {{harvnb. Gatehouse et al.. 1977