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January 21, 2018 Weekly Geology Guest, Halite

January 20, 2018
Greetings from the Bluff Park Back Porch, way up yonder on Shades Mountain (1,109′) in Alabama:
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This week’s industrial mineral is Halite or Salt.

Halite ( /ˈhælt/ or /ˈhlt/),[4] commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride (NaCl).


Halite is often used both residentially and municipally for managing ice. Because brine (a solution of water and salt) has a lower freezing point than pure water, putting salt or saltwater on ice that is near 0 °C (32 °F) will cause it to melt. (This effect is called freezing-point depression.) It is common for homeowners in cold climates to spread salt on their sidewalks and driveways after a snow storm to melt the ice. It is not necessary to use so much salt that the ice is completely melted; rather, a small amount of salt will weaken the ice so that it can be easily removed by other means. Also, many cities will spread a mixture of sand and salt on roads during and after a snowstorm to improve traction. In addition to de-icing, rock salt is occasionally used in agriculture. An example of this would be inducing salt stress to suppress the growth of annual meadow grass in turf production.
Salt is also used extensively in cooking as a flavor enhancer and to cure a wide variety of foods such as bacon and fish.[7] Larger pieces can be ground in a salt mill or dusted over food from a shaker as finishing salt.
Some cultures, especially in Africa, prefer a wide variety of different rock salts for different dishes. Pure salt is avoided as particular colors of salt indicates the presence of different impurities. Many recipes call for particular kinds of rock salt, and imported pure salt often has impurities added to adapt to local tastes.[8]
Salt domes are vertical diapirs or pipe-like masses of salt that have been essentially “squeezed up” from underlying salt beds by mobilization due to the weight of overlying rock. Salt domes contain anhydrite, gypsum, and native sulfur, in addition to halite and sylvite. They are common along the Gulf coasts of Texas and Louisiana and are often associated with petroleum deposits.

Halit (NaCl) – Kopalnia soli Wieliczka, Polska.
Halit (NaCl) – Kopalnia soli Wieliczka, Polska.


Halite cubes from the Stassfurt Potash deposit, Saxony-Anhalt, Germany (size: 6.7 × 1.9 × 1.7 cm)
Rob Lavinsky, – CC-BY-SA-3.0
Halite Locality: Stassfurt, Stassfurt Potash deposit, Saxony-Anhalt, Germany (Locality at Size: 6.7 x 1.9 x 1.7 cm. A stunning halite specimen of water-clear, stacked echelon and offset cubes. This beautiful specimen is complete-all-around and is pristine. The side views remind me of art by the famed mathematical artist, M.C. Escher. Ex. Carl Turner Collection. From the famed salt deposits at Stassfurt, Saxony-Anhalt, Germany.

Unusual halite crystals from Faiyum, Egypt
Halite from Fayum, Egypt. Collected 1989 by Wm. Revell Phillips Mineral collection of Brigham Young University Department of Geology, Provo, Utah. Photograph by Andrew Silver. No BYU index, NaCl.

Sharp halite crystals that have this green color from inclusions of malachite
Rob Lavinsky, – CC-BY-SA-3.0
Halite Locality: Lubin, Lubin District, Legnica, Lower Silesia (Dolnośląskie), Poland (Locality at Size: 10.0 x 8.5 x 5.1 cm. A fine cabinet specimen of sharp halite crystals from Poland that have this amazingly pretty green color from inclusions of malachite the halites picked up as they grew. You would swear this is a specimen of green fluorite from some new locality, unless you were to lick it and realize that it is salt (but do not lick it – natural halite specimens can harbor bacteria).

Large natural crystal of halite, showing cubic cleavage breaks
Halit (Kluftmineralisation) – Würfelförmiger Kristall mit einer Kantenlänge von 20 mm.

Pink color halite on a matrix covered with minute nahcolite
Rob Lavinsky, – CC-BY-SA-3.0
Halite, Nahcolite Locality: Searles Lake, San Bernardino County, California, USA (Locality at This is one of the largest and finest specimens we acquired from this find! Okay, halite is salt, but for one thing, it is just as legitimate a mineral as any other, even if you CAN eat it (not this though – it contains bacteria so dont lick it!). This batch of gorgeous halite specimens was mined recently in California, and they are REALLY distinctive. Look at the amazingly fine structure of the crystals and beautiful bright pink color! But more than that, they have this wonderful contrast with a uniquely new matrix covered with minute nahcolite . Bottom line: it is just a plain stunningly pretty mineral specimen from a recent find; I bought ALL OF THEM THAT WERE AVAILABLE from the one contact who brought them to a show last year in California. NOTE that they are sensitive to humidity. 13.0 x 11.4 x 5.6cm


Rob Lavinsky, – CC-BY-SA-3.0
Halite Locality: PCS mine, Rocanville, Saskatchewan, Canada (Locality at This is a really impressive, cityscape-like specimen of naturally crystallized halite. It is a floater, complete and well-formed all around! The agreegate growth is striking, in person, and it is an excellent example of the natural occurrence of what is more fondly known to the masses as “table salt,” and thus makes a good conversation piece 16.8 x 14.9 x 5.2 cm

Exquisite Blue Halite, $4,500.
The blue halite would have formed first – tens of millions of years ago. The surrounding Sylvite mineral contains radioactive Potassium 40 which has an incredibly long half-life of 1 billion years. This means the radiation is so low that geiger counters have a hard time even picking it up. Potassium 40 is also found in bananas, but the radiation is so low that it’s harmless to ingest. That being said, over tens of millions of years this low radioactivity takes its toll on the halite, effectively altering the crystal lattice which gives it its blue color. The blue is not chemical – it’s just a result of radiation on regular old table salt. The clear halite grew in more recently, and it hasn’t had time to be turned blue by the potassium in the Sylvite.

Giant Halite Cubes in Underground Salt Mine
Editors Note:  It is the intent of this site to keep this discussion as simple as possible, so as to educate the interested general public and not to discuss with the geology crowd the latest geologic theories and nuances.  Thanks, R
“No copyright infringement intended.
The rights belong to their respective owners”


We will now continue down the Industrial Mineral dusty trail and continue with Halite.
Enjoy the adventure!

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