Dolomite

Dolomite Group. Ankerite-Dolomite Series. Usually found as druzes or clusters of small rhombohedral crystals with a somewhat "saddle"-like shape, white to tan to pink in color. For dolomite-rich rocks see dolostone. Progressive dissolution–(re)crystallization reactions, leading to Ca-Mg cation ordering, are suspected to be responsible for Phanerozoic abundance of dolomite as compared to modern rock-forming environments (Pina et al., 2022).

History

Activities related to discovery and approval of the group members

Structural context

Dolomite
Crystal System trigonalCrystal Class rhombohedralSpace Group R-3
a4.7636—4.8274 (4.7955)
b4.7636—4.8274 (4.7955)
c15.582—16.3354 (16.0071)
alpha90
beta90
gamma120
volume306.214—326.922 (318.811)

Based on 112 measurements

Chemical context

Stoichiometric formulas

Dolomite
mindat.org
  • March 13, 2023CaMg(CO3)2Ca can exist in excess of up to 0.25 apfu in non-stoichiometric dolomite (Nascimento dos Santos et al., 2017).
IMA
  • March 13, 2023CaMg(CO3)2
mineralogy.rocks
  • Aug. 30, 2022CaMg(CO3)2

Elements recorded on EPMA

110
C
110
Ca
110
Mg
110
O
53
Fe
4
Mn

Physical properties

ColorColor entities, recognized using a custom trained NER model
  • colourless
  • colourless
  • reddish-white
  • brownish-white
  • gray
    Color noteOriginal color note from the source
    Colourless, white, gray, reddish-white, brownish-white, or pink; colourless in transmitted light
    StreakStreak entities, recognized using a custom trained NER model
      Streak noteOriginal streak note from the source
      White
      Lustre
      Vitreous
      Sub-Vitreous
      Resinous
      Waxy
      Pearly
      Fracture
      Sub-Conchoidal
      Transparency
      Transparent
      Translucent
      Luminescence
      None
      Tenacity
      brittle
      Hardness
      3.5—4
      Measured density
      2.84—2.86
      Calculated density
      2.876