The Olshanskyite and other minerals from Shijiangshan (Ulanhad League, Inner Mongolia, China).

May 2015

The Skarn-type deposit of Shijiangshan, Keqi County, Ulanhad League, Inner Mongolia A.R. (China) is a new location that recently yielded nice, World-Class specimens of several borate minerals.

Very few have been published so far about this mineralization, related with the famous Huanggang Sn-Fe deposit, but soon some papers will be published on this topic. The Shijiangshan deposit is very rich in boron, and the chemistry of borate is complex. In consequence, a lot of calcium borate species are chemically possible and a number of CaB minerals have been described. I think that this list will still giving beautiful species for a while. We are working on the mineralogy of Shijiangshan together with Pristine Minerals (Australia) to bring to you the best characterized specimens from this interesting deposit. Here you have a summary of the newest and more interesting results so far:

Olshanskyite

The Olshanskyite is a very rare calcium borate mineral, originally described in samples from the Titovskoe B deposit, Tas-Khayakhtakh Range, Dogdo River Basin, Polar Yakutia, Sakha Republic (Saha Republic; Yakutia), Eastern-Siberian Region, Russia. It forms small veins and crystalline masses and it has been found also in the skarns of Fuka (Okayama, Japan), where it forms centimeter size crystalline masses.

Recently, extraordinary crystals from the species were reported from Shijiangshan (Inner Mongolia, China), along with other borate minerals, particularly significant crystals of pentahydroborite. The studied crystals of alleged Olshanskyite ranged from millimeters to 4 centimeters, well formed and transparent to white. Before put it in the market and due to the exceptional size and shape for the species, we received some samples to verify the species. As usual, we used in first instance a non destructive approach and the Raman spectroscopy is the ideal technique for the identification of the borate species, as it is reliable and ultra-fast. On the contrary, usual methods based on atomic composition, as SEM-EDS, are not applicable to these species, due to the low Z of boron.

The surprise came when we found that the Raman spectrum did not match with the data published by RRUFF project and Frost et al. (2013), neither with any published Raman spectrum of described calcium borates. Maybe a new mineral?

We performed XRD and studied the thermal behavior of the crystals from China; both techniques showed exactly the same results published for the type locality and the material from Fuka. Hence we can conclude that the beautiful crystals from Shijiangshan are the same phase, described as Olshanskyite previously.

The Raman observations and the erroneous data published in both references suggested that a new, undescribed phase, are in circulation in the mineral market labelled as Olshanskyite. We tried to find it out, but, interestingly, all «olshanksyite» we located in particular collections were not olshanksyite, neither the undescribed phase used by RRUFF and Frost et al. in their descriptions. All the minerals labelled olshanskyite were other calcium borates, mainly hexahydroborite, calciborite and uralborite. Fortunately, we now have the right Raman spectrum of Olshanskyite.

Centimetric Olshanskyite Crystals

This is not surprising, because usually some dealers put in the market insufficiently characterized minerals (or, simply, they labelled the species they «believe» or what they expect will give them more profit). The problem of selling rare species identified «de visu» or without any professionalism is that the collections are filled with incorrectly labelled samples. This forces to make a great effort performing a previous characterization when we need a mineral sample for a scientific study. This is the problem with the cited paper of Ray Frost et al.: they performed the vibrational spectroscopy study of a (incorrectly) supposed Olshanskyite, trusting the original collection, without any further characterization.

This remarks the key roles of the professionalism of th e curator of a collection, no matter the size or purpose, and the risk of relaying on the seller of a rare mineral.

Wrong Raman spectrum published by RRUFF

I recommend to the collectors who own a supposed Olshanksyite to make an analytical test. Apart, I give here a clue for those interested in the hunting of new minerals: it is likely that one of the minerals used to obtain the incorrect Olshanksyite Raman spectra published by RRUFF and by Frost et al. (both are different) are a new, undescribed mineral.

The correct Raman spectrum of Olshanskyite

Johnbaumite

The Shijiangshan mine benefits a skarn very rich in boron, but the economic minerals are those of zinc and lead. The deposit have a very interesting composition that allowed the formation of World-class specimens of very rare minerals. One of these minerals is the johnbaumite , the arsenic analog of hydroxylapatite, which was described in 1980. The mineral forms white hexagonal prisms very easily confused by apatite and crystalline masses. The johnbaumite from Shijiangshan mine forms possible the best specimens worldwide.

Pentahydroborite

Another boron mineral that forms extraordinary specimens, found in Shijiangshan. The Pentahydroborite, a hydrated calcium borate originally described in the Novofrolovskoye B- Cu skarn - type deposit, was found in Shijiangshan forming euhedral crystals of centimeter size, which conforms ver y beautiful specimens. It is interesting, also, the mineral association: unexpected Andradite crystals implanted on Pentahydroborite, Wurtzite and minor Galena.

Cuspidine

We confirmed this calcium fluosilicate, easily confused with the borate minerals. It is relatively common in the

Shijiangshan deposit, forming well developed crystals and crystalline or chalky masses.

Magnetite

The well developed, centimeter size crystals of magnetite are common in Shijiangshan. The crystalline specimens we analyzed are pure, without zinc. It forms octahedrons with characteristic surface indentations.

Andradite

This garnet mineral is one of the most commonly found in the Shijiangshan mine. It forms crystals usually of sub-centimeter size, but occasionally bigger.

Andradite crystal on pentahydroborite

Wurtzite

Zinc sulfide is one of the economic minerals exploited in Shijiangshan. It forms both sphalerite and also wurtzite, which is usually associated with borates.