Rare salt formations called Mirabilite mounds have returned to the Great Salt Lake

Looking for an exciting outdoor activity? Want to learn about rare salt formations?

Mirabilite mounds have returned to the Great Salt Lake. Great Salt Lake State Park rangers are leading tours of the mounds every half hour from 11 a.m. to 4 p.m. on Jan. 23 and 24. People who want to attend must book a slot in advance online. The tour costs $3 per person in addition to a $5 fee for vehicles entering the park.
The mounds look like little terraces made of crystals. Some are three feet tall and several yards wide. They were first discovered at the Great Salt Lake by a park ranger in October 2019.
The mounds are made of Glauber’s salt, or mirabilite, which is a chemical compound that is different than ordinary table salt. Mirabilite itself is not rare, but mirabilite mounds are, according to the Utah Geology Survey. Other mirabilite mounds have been found in the Canadian Arctic, central Spain and the Antarctic.

(Photo courtesy of Utah State Parks) People who come to tour the mounds should remember waterproof shoes and a mask.

The mounds form when spring water with dissolved mirabilite in it hits cold air, according to UGS. Mirabilite is most stable at temperatures that are below freezing which is why it forms crystal mounds. When temperatures rise the crystals dehydrate and become white, powdery and easily eroded. Because the mounds only form during specific winter conditions, it isn’t clear how long they will last, according to the park.

People who want to come see the mounds should wear waterproof shoes for the tour. Masks will be required.

Research is being conducted on the mounds so the park is asking members of the public not to damage them or remove parts of them.

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