Mineralogical and Crystallographic Study of Calcite and Dolomite

1. Calcite& Dolomite
-Vishnuraayan. G.
12410034

2. Calcite – Introduction
• Most common and widespread mineral on or
near the Earth’s surface.
• Only stable form is CaCO3
• Principal constituent of Sedimentary
limestones
• Occurs in carbonate shells as fine precipitates
and as clastic materials.

3. • Color : Colorless or white, sometimes grey,
yellow, blue, red, brown

4. • Luster : Vitreous
• Diaphaneity : Transparent
to opaque
• Streak : White Streak

5. • Crystal Shape : Triagonal
• Cleavage : Rhombohedral
• Fracture : Conchoidal but rarely visible due to
perfect cleavage
• Hardness : 3.0

6. • Specific Gravity : 2.715(if pure) to 2.94
• Reaction with HCl
powdered + dil. HCl
Brisk effervescence proving presence of
carbonate group

7. Optical Properties
• no = 1.658
• ne = 1.486
• no – ne = 0.172 = δ
• Maximum Birefringence
with fourth order or
higher colors.

8. • Relief : Moderate but large variations are seen
Under PPL Under XPL

9. • Interference Figures
A normal negative uniaxial
interference figure is seen.
• Lamellar Twinning

10. Uses of Calcite
• Many different uses according to its purity and
character.
• Marbles and crystalline limestones –
ornamental stones.
• Calcium Carbonate is used as a flux in smelting
• Certain variety of calcium carbonate is used in
printing
• Lime neutralize the natural acids in the soil.

11. Dolomite – Introduction
• Occurs in extensive beds at many geological
horizons
• Dolomite may be deposited directly from sea
water, but most dolomite beds have been
formed by the alteration of limestones, the
calcite of which is replaced by dolomite.
• Chemical Composition : (CaMg)(CO3)2

12. • Color : White, yellowish, brown, and sometimes
red, green, or black

13. • Luster : Vitreous to
pearly of crystals;
dull of massive
varieties.
• Diaphaneity : Translucent to opaque
• Streak : White
• Crystal Shape : Triagonal
Presence of Mg reduces the symmetry

14. • Cleavage : Rhombohedral
• Fracture : Conchoidal
or Uneven
• Hardness : 3.5 to 4.0
• Specific Gravity : 2.86
• Reaction with HCl
powdered + dil. HCl
Does not rapidly dissolve or effervesce.

15. Optical Properties
• no = 1.679
• ne = 1.500
• no – ne = 0.179 = δ (nearly equal to that of
calcite)
• Maximum Birefringence with fourth order or
higher colors.

16. • Relief : Low to moderate or high
• Interference Figures : A normal negative
uniaxial interference figure is seen.
• Glide Twin lamellae seen on many sections

17. Uses of Dolomite
• Important Building material.
• Making of Refractory furnace lining and
source of carbon dioxide,

18. How do we differentiate
Calcite & Dolomite
• Dolomite differs from calcite because of the
presence of MAGNESIUM.
• Calcite reacts quickly with acids and produce
carbon dioxide bubbles. But dolomite, weakly
reacts with acids producing bubbles very slowly.
• Dolomite is slightly harder and denser than
calcite.
• Calcites form scalenohedrons but dolomites
never form scalenohedrons.

19. Thank You