Monohydrocalcite has been observed in air conditioning systems, and in moonmilk deposits in caves, both probably formed from spray of carbonate rich fluids.

It has been reported as a significant component of the decomposition of ikaite in the towers of the Ikka Fjord, West Greenland.

[4] It is also noted for its bizarre occurrences, which include inside the otoliths of the tiger shark, the bladder of a guinea pig,[5] the calcareous corpuscles of a cestode parasite,[6] and the final stages of decomposition of the putrefying flesh of the giant saguaro cactus.

Monohydrocalcite forms via a Mg-rich amorphous calcium carbonate (ACC) precursor.

However, the hydrated nature of monohydrocalcite means that full dehydration of Mg is not required before incorporation of this ion into this mineral and therefore it will more likely form than the anhydrous calcium carbonate phases.