Rapid Creek, Yukon, Canada
Obtained as a gormanite specimen for structure determination purpose. But the gormanite crystals are systematically twinned so that the structure determination was attempted from powder data, and was successful (to be published). The sample is not pure gormanite, and even the final synchrotron powder pattern Rietveld fit was greatly improved by taking account of three impurities (1-3% for each of them). The identification of these 3 impurities was made by using a search-match program on a powder pattern recorded from a part of the sample containing as few gormanite as possible. This is that pattern which was selected for the SMRR.
Problems on the pattern :
The sample-1 pattern presents a zeroshif which does not preclude identification. Anyway, it can be detected easily from the shift of the hkl lines of obvious phases like quartz or siderite or hydroxylapatite. We decided to not correct the pattern from the zeropoint error, in order to increase the difficulty level. Anyway, many identifications by a search-match program are made from a routine pattern, with a sample deposited on a glass sample holder so that the sample is frequently above the diffracting plane (the glass sample holder surface being exactly in the diffracting plane).
Gormanite and souzalite belong to the same series, so that souzalite is also a correct answer.
It is not impossible that the proposals of some of the SMRR participants for other minor phases in sample 1 are true (alluaudite, etc). But this would be hard to prove due to the very small contribution to the pattern.