Rare mirabilite formations spotted on Great Salt Lake

This article is published through the Great Salt Lake Collaborative, a solutions journalism initiative that partners news, education and media organizations to help inform people about the plight of the Great Salt Lake—and what can be done to make a difference before it is too late. Read all of our stories at greatsaltlakenews.org.

GREAT SALT LAKE, Utah — Rare mirabilite formations were recently spotted on the waters of Great Salt Lake. 

According to the Utah Division of State Parks, the rare mirabilite formations can only be found in a few areas; the Canadian Arctic, Antarctica, Central Spain, and Utah. 

The Utah Geological Survey said that mirabilite mounds form when water rich in sodium sulfate comes into contact with cold air. Crystals stick together, creating mounds. The mounds are composed of hydrated sodium sulfate, commonly known as Glauber’s salt. 

Mirabilite is common and found in saline lakes all over. Crystals form and reach the water’s surface, eventually washing ashore. 

However, the mirabilite formations spotted on Great Salt Lake on Nov. 21 are rare. The Utah Division of State Parks said underground springs containing a lot of sodium sulfate caused them. 

The Utah Geological Survey said they are rare because they are spring-fed. Their first recorded appearance on the lake’s waters was in October 2019, per the survey’s website. 

Mirabilite formations will eventually disappear from the water’s surface. Warmer water temperatures could erode them, reducing them to thenardite. Alternatively, rising lake levels could reduce them. 

Since their appearance relies on highly specific conditions, it is unknown if or when they will reappear on the lake. 

Fragile, view carefully

The Utah Division of State Parks’ Facebook post asked visitors to be careful around the formations. They are very fragile. 

Visitors are asked to view them from a distance and avoid walking on them. Also, do not remove any crystals from the formations. 

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