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Probertite
NaCaB5O7(OH)4·3H2O monoclinic
At most localities, Probertite occurs as prismatic crystals that commonly are found in intergrowen radiating bundles in massive ore and only rarely exhibit well defined crystal faces. It has been found at fewer than 20 localities but at some of these localities it is abundant and in the borates ores at these localities represents hundreds if not thousands of tons of the mineral. However at the Kohnstein Quarry in Germany, they are found as well formed transparent crystals, some of which you could cut transparent faceted stones from (God forbid!). This German locality would have to be rated as producing the best crystals by one or two orders of magnitude.
Probertite
Germany
Thuringia, Harz Mts, Nordhausen, Niedersachswerfen, Kohnstein Quarry
Free standing Probertite crystals were only found once in the Kohnstein Quarry in a series of small pockets in massive Anhydrite. This was in 1996/97. They occurred as white, clear terminated prismatic crystals up to about 10 cm in length but the larger crystals were laying flat on the matrix but the best crystals were smaller up to about 4.8cm. It was impossible to get free standing crystals on matrix due to the massive, hard nature of the anhydrite rock. Only a few terminated crystals were found and perhaps the best terminated crystal measured 4.8cm and can be seen above in Picture #1. Less than 20 good probertite crystals of more than 2 cm were found, plus 2 handful material of smaller crystals, crystals without termination and fragmented crystals (due to the very good cleavage parallel to the elongation), plus 5 - 6 flats of samples with flat laying crystals on matrix. Fibrous or radiating probertite, known from other borate deposits, were not found. A few other well crystallized borates were also found at this locality, perhaps most notably Priceite and Hydroboracite. Usually the clefts and veins that are borate rich produce only one borate mineral. Hydroboracite was much more common, and was found more or less continuously over several years. All the other borate minerals are very rare and only a few samples were found, e.g. from tuzlaite only one sample on matrix and some small loose crystals are known.
The Kohnstein Quarry, Niedersachswerfen, is an anhydrite quarry mined several years for anhydrite and now inactive.
In the active time, in the anhydrite sometimes borate minerals were found in clefts, small veins and lenses. The main borate minerals is hydroboracite.
[Thomas Witzke 2009]
Probertite
Turkey
Marmara Region, Balikesir Province, Bigadiç, Bigadiç Mine
We need someone to tell us about Turkish Probertite specimens.
Probertite
USA
California, Kern Co., Kramer District, Boron, U.S. Borax Open Pit Mine
There were some other flavors of Probertite specimens that were found at Boron and eventually we should have some of them pictured here, but compared to the German crystals they are nothing to write home about. Most of the specimens, and there were tons of them mined, are radiating star like masses found low in the deposit below the borax. Perhaps the best of them did not look any better than the one above in picture #6. They are certainly will not cause any collector to loose any sleep if he/she does not have an example of it in their collection.
Probertite
USA
California, Los Angeles Co., Lang, Tick Canyon, Lang Mine (Sterling Mine; Tick Canyon Borax Mine)
The Probertite specimens from Tick Canyon have been available to local collectors from Los Angeles for years and undoubtedly several tons of them have been hauled away and placed in collection drawers, boxes in garages and in flower gardens. Most of the stuff that has been hauled out of the borate locality at Tick Canyon has been nodules of Howlite that had some small desirability and value for lapidary purposes. The Probertite specimens from this locality are not much in demand and most of them that were collected there were probably mistaken for Howlite nodules. The one shown in picture #7 is a good example of a typical specimen. They get larger, but not better and for that matter not much worse either.
Rock Currier
Crystals not pistols.
Edited 5 time(s). Last edit at 07/13/2009 07:36PM by Rock Currier.
