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Blue Halite / Carlsbad NM / real or fake?

Posted by John Krygier  
John Krygier August 17, 2009 10:29PM
Hi all,

This item was identified as Blue Halite from Carlsbad NM. Zoning at several different angles,
and purple rather than blue on one end. The wood cube in the pictures is 1 inch square.

After I bought it I wondered if it could be fake? Can blue halite be faked?


open | download - halite_blue_1.jpg (511.5 KB)
open | download - halite_blue_2.jpg (498.6 KB)
open | download - halite_blue_3.jpg (479.5 KB)
Kelly Nash August 18, 2009 12:57AM
It's real. I have several nice specimens purchased directly from miners. I'm not sure the cause has been determined for sure. Crystal lattice defects, possibly from radiation, maybe not. I understand people have tried turning clear halite blue in a lab using radiation, but have not been able to do so.
Michael Hopkins August 18, 2009 02:52AM
I have always understood the color was caused by bacteria or some other organic material.

Edited 1 time(s). Last edit at 08/18/2009 02:53AM by Michael Hopkins.
Richard Dale August 18, 2009 03:12AM
I just happened to be reading a Caltec article on the subject... "Blue halite from Germany is the result of exposure to natural radiation. Initially, if halite (common salt) is exposed to gamma radiation, it turns amber because of f-centers. They are mostly electrons trapped at sites of missing Cl- ions. In time the electrons migrate to Na+ ions and reduce it to Na metal. Atoms of Na metal, in turn, migrate to form colloidal sized aggregrates of sodium metal. They are the cause of the blue color." From http://minerals.gps.caltech.edu/COLOR_Causes/Radiate/ : In the case of Carlsbad, I heard that it came from decaying K40 in the Sylvite. RD
Philip Simmons September 05, 2012 09:30PM
I just ran across this question today.

Richard is right on point. The blue and purple color is caused by the radiation effects of K40 decay from surrounding sylvite. I have communicated with Dr. George Rossman on this subject, and am in the process of completing an article that covers this phenomenon in more detail.

I have field collected many of these halite crystals, and they always seem to have sylvite very close by. Many of the pictures seen on Mindat and elsewhere that are labeled "blue halite crystal in clear halite" (or something along those lines) are, in fact, blue halite frozen in colorless SYLVITE. I just collected an interesting piece this past weekend that has crystals of both species growing together, and the only area where the halite is blue is the crystal boundary between the halite and sylvite. The easiest way to differentiate between the two minerals is to taste them...seriously!!! The halite will taste like common salt and the sylvite will have more of a "bite" or bitter taste to it if left on the tongue for a couple seconds.

As for the article, maybe we'll see it sometime in the near future! ;-)

Philip Simmons
Mining Engineer in Carlsbad, NM
Franklin Roberts September 21, 2012 12:43AM
Carlsbad was the site of Project Gnome, a 3.1 kiloton underground nuclear detonation in 1962. A lot of multicolored halite was created by the blast and subsequent irradiation of the salt bed in which the shot was fired.


Have you checked to see if your specimens carry any residual radioactivity?

Gary Jessey September 23, 2014 01:56PM
I have a question:
How can you keep Blue Halite Dry (as well as any other Halite)?
Rob Woodside September 23, 2014 04:39PM
In a dry climate just leave it on the shelf. In a humid climate you might keep it covered and with some desiccant. Sealing in a container seems like overkill.
Nelse Miller September 23, 2014 04:41PM
Decades ago I remember reading that blue halite had the same visible absorption spectrum as a fresh solution of sodium metal in liquid ammonia. I remember that blue color from a lab experiment using the sodium solution as a powerful reducing agent in an inorganic synthesis.. At the time the blue color was attributed to "solvated" electrons and that the color didn't depend on which alkali metal was used. Sodium, potassium, rubidium and cesium gave essentially the same spectrum. However, that was forty years ago and it is not a subject that I have followed.
Michael Hatskel October 11, 2014 06:11PM
By itself, the blue color of halite grains/crystals in mined rock salt is not unusual at all. I would guess that it's probably the combination of the blue and purple colors that started the thread. Is it known where the purple comes from?

Also, there were no responses to the question asked by Franklin Roberts in his September 20, 2012 post. Does anyone have any input on that?
Rob Woodside October 18, 2014 02:56AM
The purple is probably due to an occupied colour center as with purple sodalite. The blue is supposed to be colloidal native sodium!
Doug Daniels October 18, 2014 04:34AM
I've always wondered....if the radiation splits the molecule to make colloidal native silver, what happens to the chlorine? Native colloidal chlorine?
Peter Haas October 18, 2014 10:08AM
Radiation does not split any molecules, because there are no molecules in a halite crystal. Instead, radiation cleaves electrons from chloride ions (leaving chlorine radicals behind) which are then trapped by sodium ions. The chlorine radicals may combine to form chlorine, Cl2 (i.e. "native" chlorine), react with sodium atoms to form sodium ions and chloride ions (this reinstates the original situation, but will produce heat, so in the overall reaction the radiation was converted into heat) or stay trapped as chlorine atoms (or chlorine radicals, which is the same) on their lattice positions.
Steve Hardinger October 18, 2014 03:50PM
So Peter what then happens to the Na+? Does it remain as such (and so the halite lattice begins to collect an overall positive charge) or os the Na+ reduced to Na?

BTW, the characteristic color produced when an alkali metal (Li, Na, K) is dissolved in liquid ammonia is due to the solvated electron. But other species can produce an identical color, for example, a solution of benzophenone and Na in THF.

/chemistry lesson
Rob Woodside October 18, 2014 05:24PM
Antozonite, http://www.mindat.org/min-30325.html, has native Fluorine, but no one bothers to write it up and have it rejected by the IMA. The prejudice for structures with sharp x-ray diffraction patterns is so great that even Hg could be discredited if anyone bothered to write it up.
Doug Daniels October 18, 2014 05:42PM
Rob, so that means I have to get rid of my specimen of native oxygen and nitrogen? Dang.
Rob Woodside October 18, 2014 06:39PM
No Doug, just relabel them with IMA rules in mind. Unfortunately most native oxygen is mixed with native nitrogen, with native nitrogen dominant, and so by the 50/50 rule should be referred to as native nitrogen:-D

Years ago at the Science Museum in London they had a display of the periodic table populated with samples of the elements. It was very interesting but I was amused by the apparently empty vials that contained the noble gasses. Currently you can buy Ar filled double windows that for some unknown reason are supposed to have a lower thermal conductivity than air filled windows. Short of inducing electric discharges in the enclosed gas I have no idea how to tell if the Ar is there. I would be surprised if it was.
Erik November 11, 2014 12:13AM
Does the radiation explanation also apply to the blue halite I have dug up from Searles lake? I was told it was from the clay and bacteria in the trench which it grows in. Sorry, in the photo it looks green, but it's an aqua blue.

open | download - blue halite copy.jpg (900.4 KB)
Rock Currier November 11, 2014 06:33PM
I have never seen blue halite from Searles lake. Can you supply a picture?

Rock Currier
Crystals not pistols.
Peter Haas November 11, 2014 07:21PM
Steve Hardinger Wrote:
> So Peter what then happens to the Na+? Does it
> remain as such (and so the halite lattice begins
> to collect an overall positive charge) or os the
> Na+ reduced to Na?

I don't see your problem. Charge is perfectly balanced, irrespective whether or not the electron gets trapped:

Cl- -> Cl* + e-
Na+ + e- -> Na

There's no guarantee that the electrons get trapped by sodium ions only because there's an electrostatic attraction. Electrons cleaved by photon impact can leave in any direction and with a wide range of kinetic energies. Plus, they are very low mass particles and therefore easily tunnel at a finite chance across electrostatic energy barriers.

By the way, "quasi-free" electrons (i.e. those that are trapped on interstitial positions) are prime examples for the quantum-mechanical "particle-in-a-pot" problem in that their energy states will only depend on the symmetry of the potential energy pot (i.e. the charge distribution in the lattice). Therefore, free electrons in halite always cause a yellowish-green colour, no matter where the electron came from. Likewise, in sylvite, they always cause a purple colour.
Reiner Mielke November 11, 2014 08:14PM
Maybe someone lost their blue pen at Searles Lake?
Doug Daniels November 12, 2014 12:48AM
Or, stay the heck away from that place! Unless you're trying to sterilize something.....
Vitaliy November 19, 2014 01:54AM
Usually the color of Halite from Searles Lake is that of a Pinkish color. I have never seen a Blue halite from Searles Lake.
Rock Currier November 19, 2014 06:10AM
Most of the halite from Searles lake is not a pink color unless it has been dipped in a bucket of brine that has been spiked with a gallon of red food die #1.

Rock Currier
Crystals not pistols.
Wayne Corwin November 19, 2014 12:36PM
Geeee Rock,,,, that sounds fake :)-D
Vitaliy November 19, 2014 03:30PM
Rock Currier Wrote:
> Most of the halite from Searles lake is not a pink
> color unless it has been dipped in a bucket of
> brine that has been spiked with a gallon of red
> food die #1.

It seems as if Halite from Searles Lake is either White or Pink sometimes with brine red samples from a quick Google search. I have also seen White hoppered Halite crystals on a pink matrix from Searles as well. Pink Halite is just as common as White Halite from Searles Lake.

Speaking of Searles Lake I would love to go collecting there one day for cabinet Halite pieces along with the Great Salt Lake in Utah.
Uwe Kolitsch January 27, 2015 10:46AM
A spectroscopic study of blue halite from Poland:

Sylwia M. Zelek, Aleksandra Wesełucha-Birczyńska, Janusz Szklarzewicz, Katarzyna M. Stadnicka (2015): Spectroscopic properties of halite from Kłodawa salt mine, central Poland. Mineral. Petrol. 109, 45-51.

The dynamics of colour centre transformation was investigated in blue halite single crystals from Kłodawa Salt Mine, Central Poland, using UV–vis spectroscopy. The following colour centres were considered: F, R1, R2, as well as plasmons and M centres. The R2 centres predominated in navy blue (A) and pale blue (B) halites. Other relatively large populations were plasmons found in all examined samples. In purple (C) halite samples the plasmon population is the highest one among others and R1 centres appeared to be equally significant, whereas M centres were almost absent. For A and C samples unidentified bands were observed at 26,500 to 26,200 cm−1, respectively. The bleaching process of the blue halites was investigated using temperature dependent UV–vis and micro-Raman spectroscopies. In micro-Raman 300–100 cm−1 region three very intense sharp bands were attributed to the colour centres and colloidal Na precipitation in A and B halites. The one broad band in the range 3,500 to 500 cm−1, which was characteristic even for the colourless sample D but absent in the spectra of colourless NaCl obtained after recrystallization of sample A, requires further study.
Reiner Mielke January 27, 2015 03:55PM
So Rock are you saying all the pink halite from Searles Lake is fake? I've noticed some of it has a strong fish smell is that normal?
Marek Chorazewicz January 28, 2015 11:58PM
I guess the mechanism is different between the pink and the blue halite.

I've found pink hoppered crystals and dark pink cubic crystals in a dark red brine pool at the Searles Lake Gem-O-Rama last October. My son was digging 30 meters away in a hard whitish pink crust. He got to a colorless brine underneath the crust and found completely white cubic crystals there. The halite from layers deeper in the lake (from blowhole trip) is colorless as well.

The presentations we saw there stated that the pink color is due to the halobacteria living in brine pools. When the bacteria die from dryness or sun exposure the halite will lose its color.

Best Regards,
Rock Currier February 20, 2015 07:22AM
No, some of it is real. But even the natural pink material will fade out over time.

Rock Currier
Crystals not pistols.
Harley Alton September 06, 2017 10:27PM
I work in a potash mine and have found pounds and pounds of this stuff... it's very real.
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