This is a very good example of syntactic intergrowth of mckelveyite-(Y) with donnayite-(Y) (or perhaps an intermediate member of the mckelveyite-donnayite series). MSH is the type locality for donnayite-(Y). It is uncommon, but not rare here. Mckelveyite-(Y) is rare. However (as is generally the case at MSH) this is neither “end member” donnayite-(Y) nor “end member” mckelveyite-(Y). From a similar specimen from this find, significant Ba and Sr are both present. While peak heights can not be directly compared in a qualitative scan such as this, it does suggest that mckelveyite-(Y), rather than donnayite-(Y), might be the dominant component. But the system used detects Ba more readily than Sr, so WDS would be needed to be sure. Also, XRD might be needed to eliminate ewaldite as another possibility. My best guess is that this is an intergrowth of mckelveyite and donnayite.

All of the “mckelveyite/donnayite” on the specimen is shown in the first pair of photos (FOV 2.4 x 2.9 mm). The individual “cones” are <= 0.4 mm in diameter. Note the tiny pyrite “sprinkles”, some of which may have affected the EDS scan.

Single item shipping weight (with mini TN case) is 3.1 oz (88 g). 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 Priority Mail ($7.25 - $9.20 including packing – varies by destination).