Bromlite
Synonym: Alstonite.
Chemical: BaCa(CO3)2, sometimes strontium.
Mineralogy
Hydrothermal mineral.
Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous.
Alstonite is triclinic.
Barytocalcite is monoclinic
Paralstonite is trigonal.