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"Golden" halite cubes in Carlsbad postash mine

Source : Armando Perrini

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Rocksalt - Steinsalz - Sel roche - Sal

America : USA : Carlsbad : Giant "golden" halite cubes

Coordinates : aprox. 32°27'N , 103°53'W :
PCA = Eddy Potash Mine, Carlsbad, Eddy Co., New Mexico, USA

The crystallisation of large halite cubes is a rather common process, which can be studied in detail in many salt mines worldwide. In fact, it is often a surprisingly fast process, where 10 cm or even larger crystals can form in some years or even only months time. However, the formation of giant halite crystals in the 1 m range is by far rarer. Apart from the well documented and readily accessible Merkers potash mine in Thuringia and some rumours about other giant halite cubes in northern Germany the "golden" halite cubes of the PCA mine near Carlsbad seems to be the only other well known example.

The potash deposits of the Carlsbad area are of permian age, similiar to most european potash deposits. Mineable potash seamd occur intercalated with halite and other evaporites and are generally little affected by any tectonics. They are however subject to highly pressurized natural gas in the overlying beds. To prevent extensive. roof falls caused by the pressurized gas, the gas is vented by regular drills into the ceiling.

In April 1962, a drill hole encountered a large cavity full of brine, which immediately rushed down into the adits and stopped hours later only. Mr. Perrini, the mine foreman at that time, decided to investigate the brine inflow and ordered to drive a raise, which finally hit a large, though very flat cave with the giant halite cubes shown here. Some months later a second similiar cave was discovered with even larger halite crystals as well as some exceptional large sylvite crystals.

Little is known about the further fate of this crystals, though some smaller ones were recovered by the miners. As potash mines are often subject to (catastrophic or systematic) flooding, it appears that either the cystals have been dissolved since many years or they are in danger to do so in the near future...

P.S. : The remarkable "golden" colour of the crystals originates from finely dispersed iron oxides, which are quite common in these deposits.

Update April 2006 : The mine was later bought by Eddy Potash Inc and was known as the Eddy mine until its final closure due to depletion of high grade potash ore in December 1997. In the moment there are plans under way to flood the whole mine and convert it into a salt brine production facility. This will definitely mean the loss of any remaining crystals !


Discovery of the giant halite cubes in April 1962
Source : Armando Perrini

Detail of a halite cube, reaching about 1 m size
Source : Armando Perrini

Other notable & famous halite occurences :

- Cubes to 1 m size has been discovered in the Merkers potash mine, Thuringia, Germany, which can be visited as part of an touristic mine tour. For more information please look here. Other large halite cubes have been rumoured to occur in other german potash mines as well, such as the long abandoned Allertal mines.

- rose to pink coloured, often skeletal cubes, are formed in recent salinas such as the Searles Lake, San Bernardino Co, California. The colour is due to haliforom bacteria and often starts to fade after some time.

- Fine transparent halite cubes up to 0,5 m size are known from the famous Wieliczka mines near Krakov, Poland, a world heritage site.

Carlsbad Potash Mines Essentials :

Mineralogy :


Crystal Size :

Maximum size of crystals is about 1 m

Geology & Origin :

Crystallization from oversaturated brines in open vugs, formed by pressurized gas

Current status :

Not exactly known, possibly still in place. The mine itself was closed end of 1997.

Remarks :

More information about the site is needed.
Ressources and relevant weblinks :

There is an excellent publication about the history and geology of this spectacular find, which was published in the Mineralogical Record magazine in 1999 :

MINETTE, JAMES W. (1999) : Great Pockets : The Carlsbad Halite Caves; in :
Mineralogical Record, Vol. 30; September - October 1999, pp.369 - 372.

Courtesy of the Mineralogical Record you are able to read the full story here.



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