Report on the activities in the ruby project 2012. A joint project with the Bureau of Minerals and Petroleum

This project on the evaluation of Greenlandic rubies is part of a collaboration project be-tween the Bureau of Minerals and Petroleum in Nuuk, Greenland and the Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark. The investigations are mainly aimed at the characterisation of the Fiskenæsset complex rubies, because the most promising ruby outcrop in that area, Aappaluttoq, is likely to be mined in the nearest future by the Canadian company True North Gems (TNG). In the second year of the project on Greenlandic rubies the activities concentrated on the analytical investigation of the rubies collected in the Fiskenæsset complex in the summer of 2011 and on the presentation of the Greenlandic ruby occurrence to the interested public.

In the summer of 2011 Per Kalvig (GEUS), Henrik Stendal (BMP) and Anette Clausen (BMP) collected circa 50 rock samples from 8 localities in the Fiskenæsset complex with the aim to characterise the Fiskenæsset complex ruby occurrences using the gemmologi-cal, geochemical and optical investigations (see Kalvig & Keulen, 2011).

From the collected material 32 samples were selected. These samples were crushed and the rubies larger than 2 mm were collected and described for their colour, transparency, size and other characteristics (see Kalvig & Keulen, 2011). 20 of the samples and 2 other samples (one from Walton’s showing (Qaqqatsiaq) and one form southeast of the Bjørnesund near TNGs Qororssuaq locality hence called Qororssuaq East) have been investigat-ed with the Energy Dispersive X-ray Spectrometers (EDX) of the Scanning Electron Micro-scope (SEM) at GEUS with the aim to chemically characterise the mineralogy of the inclu-sions in the rubies and with laser ablation sector-field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS) at GEUS in order to investigate the trace element distribu-tion. These investigations will be reported in Chapters 2 and 3 respectively.

Ruby samples from the Fiskenæsset complex are generally rich in mineral inclusions and a whole suite of different minerals has been observed. The samples from Aappalutoq, however, are not very rich in mineral inclusions. Anorthite inclusions, when they are observed, probably are a good characteristic of the Fiskenæsset rubies, as this type of inclusions does not occur often in rubies from other localities. Other mineral inclusions cannot be used to characterise the Fiskenæsset complex very well, but are important clues in the understanding of the metamorphic processes that formed the rubies. A good comprehension of these processes might enable us to predict where to search for further occurrences of rubies or sapphires.

Trace element investigations with a LA-ICP-MS instrument appears to be a promising tool in the fingerprinting of the Greenlandic ruby. Based on the trace elements (Mg,) Si, Ti, (V), Cr, Fe, and Ga for the highest quality samples from Aappalutoq, it seems possible to dis-tinguish these from 25 internationally known ruby occurrences. For a most effective fingerprinting a combination of trace element analyses, oxygen isotope analyses (see Kalvig & Keulen, 2011) and other studies need to be performed with for example multivariate statistics. It should be stressed that the ICP-MS study ought to be confirmed on gemstone quality rocks in the future as trace element patterns are not exactly the same for low and high quality stones.

We performed some preliminary Raman Spectroscopy analyses at the DTU, which are reported in Chapter 4. Analyses were performed to characterise the Greenlandic rubies with a non-destructive method. The preliminary conclusion of these investigations is that Raman spectrometry does not work very well on ruby samples that are relatively rich in the trace element chromium, as is the case for the Fiskenæsset complex samples. However, more work on Raman and other types of spectroscopy will be performed in 2013.

On the 12^th-13^th December, Nynke Keulen (GEUS), participated in “The 3^rd International Gem and Jewlry Conference” in Bangkok, Thailand. The conference and associated excursion were organised by the Thailand public organisation the Gem and Jewelry Institute of Thailand (GIT). The excursion on the 14^th – 16^th December visited Chanthaburi (Eastern Thailand) and Pailin (Cambodja). From BMP Thomas Lauridsen and Lærke Louise Thomsen participated. Before the conference, two jewelry sellers were visited in Bangkok. During the conference and excursion, three cutting facilities, a heat treatment facility and three small scale miners were visited. These visits, information obtained during our stay in Thailand and the abstracts of the conference oral presentations were summarised in a separate note (to be released by BMP). A copy of the PowerPoint presentation and the extended abstract by Nynke Keulen & Per Kalvig, with the title: “Oxygen isotopes and geochemical characteristics of corundum (ruby) from Fiskenæsset, Greenland – identification and origin determination” are included in the appendices to this report.

The initial findings for the characteristics of the Fiskenæsset complex will be published by Nynke Keulen and Per Kalvig in the Review of the Surveys Activities under the title: “Identification and origin determination of corundum (ruby) from Fiskenæsset, Greenland”. This article is expected to be published later 2013. The draft version of the text is appended to this report.

This report refers to corundum, pink sapphire and ruby as rubies irrespective of the quality of the stone or the intensity of the red colour.