Yangzhumingite (2009-017) in press

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Miyawaki, R. et al.:
Yangzhumingite, KMg2.5Si4O10F2, a new mineral in mica group from Bayan Obo, Inner Mongolia, China.
European Journal of Mineralogy

Yangzhumingite, ideally KMg2.5Si4O10F2, occurs as subhedral to euhedral platy crystals up to ca. 0.5 mm across in metamorphosed carbonate rock from Bayan Obo, Inner Mongolia, China. It is associated with dolomite, calcite, tremolite, norbergite and huanghoite-(Ce) with minor phlogopite, barite, bastnäsite-(Ce), parisite-(Ce), and fluorite. Yangzhumingite is transparent and colorless with white streak and pearly luster. It is optically biaxial (–), n = 1.532–1.537 (589 nm), and 2V = 5–10°. The hardness is 3 on Mohs’ scale (measured on a synthetic equivalent). It has a monoclinic unit cell with a = 5.249(4), b = 9.095(5), c = 10.142(5)Å , β = 99.96(6)°, V = 476.9(5)Å3, Z = 2, space group C2/m, and Dcalc. = 2.807 g/cm3. The five strongest lines in the powder XRD pattern are [d(Å), I/I0, hkl]: (10.03, 95, 001); (3.37, 48, 022), (2.90, 49, 11–3), (2.59, 67, 13–1 200) and (2.41, 100, 13–2 201). The mean of 15 electron microprobe analyses and SIMS analysis for Li lead to the empirical formula (K0.70Li0.30Na0.01)(Mg2.48Fe0.06) (Si3.96Al0.03)O10[F1.92(OH)0.08] on the basis of 12 anions with (F + OH) = 2. Yangzhumingite is a member of the mica group (Nickel-Strunz grouping 9.EC.10), and it represents the Mg-dominant analogue of montdorite.

Interesting mineral. The first I heard of it was from Yang Zhuming just as we were passing througn a mountain pass just after having traversed a section of the Great Wall in the middle of no where. This is an example of examining any rock you can get at some Chinese locations as collecting is practically forbidden at Baiyun E'bo.

I am found Yangzhumingite in my old specimen of Tainiolite from Bayan Obo. Its composition is K_1.03(Mg_2.29Li_0.21Fe_0.05Mn_0.03)_2.59[Si[sub]2[/sub]O₅]₂F_2.00 (Li content was calculated according to electric charge balance). This is the second occurrence of Yangzhumingite on the locality in association different from one described by Miyawaki e.a. Associated minerals here are green prismatic Aegirine, Magnetite, abundant Thorite, unusual bright-pink Zircon, Fluorite of two generations and K-Feldspar. This old specimen was collected in 50th. Yangzhumingite form here large (up to 1 cm) bronze plates.



Edited 1 time(s). Last edit at 05/23/2012 11:41PM by Pavel Kartashov.

Yangzhumingite has also been found at a locality at Kvaløya, Troms in Norway, see [www.mindat.org].
It was recognized in a thin section of a lamproite dike crossing a granite of 1,8 Ga age. The find has been published in the University of Tromsø's popular magazine "Labyrint".
A pdf of the magazine (in Norwegian) with photos can been downloaded here ( the article is on p. 6):

[uit.no]