This specimen is from a find that produced khomyakovite, manganokhomyakovite and ferrokentbrooksite (all verified via WDS). However, most crystals were found to be zoned with ferrokentbrooksite cores and khomyakovite or manganokhomyakovite shells – or just plain ferrokentbrooksite alone. It is impossible to distinguish the various possibilities visually.
A qualitative EDS scan for this sample shows the presence of W. (See the “Analysis” tab.) The W peak may not look very impressive, but, according to the analyst, the high energy peak of W is relatively hard to detect with his equipment , so it is actually “significant”. (The low energy W peak is “buried” under the Si peak.) If the W is in the proper structural site and there is enough of it, this could be khomyakovite. If not, it is probably ferrokentbrooksite. EDS is not sufficient to decide. WDS – very expensive – would be needed. Khomyakovite is extremely rare. Ferrokentbrooksite – not so much.
Of the half dozen or so specimens from this find which I was fortunate enough to have properly analyzed, about half had khomyakovite or manganokhomyakovite, the rest only ferrokentbrooksite. If you think of this as a lottery ticket, that’s pretty good odds. But it isn’t a guarantee.
The specimen features several small, but well formed crystals to about 0.8 mm. You will need 20-40X to view them clearly.
The first photo (FOV 3.0 x 2.1 mm) shows two sharply formed crystals to about 0.8 mm on the right. The group on the left consists of smaller crystals, only one of which seems to be sharply formed.
The crystals show in the other two close-up photos (FOV 1.9 x 1.8 mm and 2.2 x 2.3 mm resp.) are both sharply formed but only a bit < 0.6 mm in diameter.
Single item shipping weight (no case) is 3.3 oz. For shipments outside the USA, up to a total weight < 8 oz (225g), this can be combined with items from this or other auctions for the same postage.
Within the USA, postage for total weights up to 13 oz ranges from $4.25 to $6.50 (including packing etc) regardless of destination. Above 13 oz, I will use “own box” Priority Mail. The rate, including packing, varies by destination from $7.25 to $9.50.
See my updated “Shipping Policy” for details.
