As followers of the post continued to guess what the mineral might be, officials replied in a comment that officials are “skeptical of what it really is.”

“Foreign metals were introduced to the area by means of garbage left in the mine,” they said. “Tin, Zinc, Lead, Iron, and other metals that were left in the water would have the opportunity to precipitate into the water and through a very slow process join to other metals.”

Adventure Mine owner Matt Portfleet told Michigan Live that the third level where the mineral was found was filled with groundwater up until this past fall when his crew finished pumping out water. As he and his workers explored the newly accessible level, he says they found “small patches of a bright blue mineral on the freshly exposed rock.”

He said it would be difficult to positively identify minerals like this as they can quickly decompose when surrounding water is removed, according to Michigan Live.

Adventure Mine operated from 1850 to 1920, according to its website, as “miners removed more than 11 million pounds of native copper from the ground.” There are 13 levels to the mine, though mine officials say their pumping equipment will not go much further down.

The township of Greenland is in north Michigan, just south of Lake Superior.

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