Mineral Information and Data:

BaCa(CO3)2 [CNMNC approved formula]

Named in allusion to the composition, containing BARium and CALCite.

IMA status : Valid species (Pre-IMA 1824) Grandfathered
(8th edition) :  
  (14) Anhydrous Carbonates
  (14.02) with Compound Formula A+ B++ (CO3)2
(10th edition) :
  (05) Carbonates and Nitrates
  (05.A) Carbonates without additional anions, without H2O
  (05.AB) Alkali-earth (and other M2+) carbonates
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: P21/m
Unit cell: a = 8.13Å, b = 5.22Å, c = 6.54Å; β = 106°
Crystal Habit: Typically as elongated crystals, short to long prismatic and striated parallel [101], to 5 cm, or equant, showing large {100}, {111}, {131}, {210}, minor {001},{110}, {101}; may be massive, cleavable.
Color: Colorless to white, pale gray, bright to pale green, pale yellow; colorless in transmitted light
Diaphaneity: Transparent to translucent
Luster: Vitreous to resinous
Hardness (Mohs): 3.5 - 4
Measured Density: 3.66 – 3.71 g/cm3
Cleavage: On {210}, perfect; on {001}, imperfect
Fracture: Uneven to subconchoidal
Polymorphism and Series: Trimorphous with alstonite and paralstonite.
Geologic Setting: A relatively uncommon accessory mineral in metallic veins, formed by reaction of hydrothermal fluids with limestone; however it may be the dominant barium-bearing species; rarely in carbonatites and Alpine veins.
Mineral Association: Baryte, calcite, strontianite, siderite, alstonite, benstonite, witherite, norsethite,
fluorite, sphalerite, pyrrhotite, quartz
Luminescent Properties: Pale yellowish to red fluorescence under SW and LW UV.