This presentation is about the basic concept of Dolomite petrography, while studying thin section of dolomite , and you maybe similar result as shown in presentation.

1. Dolomite
Petrography
By
Muhammad zarak

2. Dolomite Petrography
• Petrography; The systematic description of geological
materials and their composition in hand specimens and
thin sections.
• Someone who studies petrography is called a
petrographer.
• While Dolomite petrography mean that
minerological,compositional and thin section study of
Dolomite.

3. Dolomite Petrography
Dolomite petrography includes:
• Stoichiometry
(if its a stoichiomitric dolomite)
• Non-stoichiometric dolomite
• Zoned dolomite
• Limpid dolomite
• Xenotopic dolomite
• Idiotopic dolomite
• Hypidiotopic dolomite
• Hollow dolomite
• Dedolomite

4. Dolomite Petrography
• Stoichiometric dolomite:
In contrast to high-magnesian
calcite, true dolomite, so-called
stoichiometric dolomite, is a
totally different mineral in which
Mg ions occupy half of the cation
sites in the crystal lattice and are
arranged in well-ordered planes
that alternate with planes of C03
ions and Ca ions.

5. Dolomite Petrography
• Zoned Dolomite:
• (A)Euhedral dolomite crystals with cloudy
cores and clear rims.
Note ghosts of fossil fragments in some of the
cloudy cores.
James & Jones, 2015
• (B)Euhedral to subhedral dolomite,
Zoning is not readily visible because it consists
mainly of
slight elemental variations. In such cases,
staining,
cathodoluminescence, backscattered electron
imaging or
other techniques can be used to accentuate
zonation.

6. Dolomite petrography
Dolo Calc Fe-Dolo Fe-Calc
Alizarine - red - red
K-ferricyanide - - blu blue Blue
Aliz. + K-ferry. - red blue purple/Deep Blue
Zonned dolomite

7. Dolomite Petrography
• Limpid Dolomite
• An example of mixing zone
dolomite cements in a
Pleistocene wackestone.
Calcite is stained red and
dolomite remains unstained.
Note the limpid (very clear, nearly inclusion-free) character of the
cements and the thin, interlayered bands of low-Mg calcite cements
growing in continuity with the dolomite. Clear pore space remains at
the center of the pore. Photograph courtesy of John D. Humphrey.
PPL, AS, HA = 1.2 mm

8. • Closely packed with
mostly irregular
crystalline
boundaries.
• Most
dolomite
crystals
are
Euhedral
rhombs.
• Most dolomite are
subhedral to Andhedral
with straight
compromise
boundaries and many
crysstal face junctions.
Xenotopic dolomite /Idiotopic dolomite /Hypidiotopic dolomite :

9. Dolomite Petrography
• Hollow dolomite:
Hollow dolomite rhombs and
rhombohedral pores form due
to dissolution of the cloudy
cores or the whole dolomite
rhombs, respectively and
filling of hollow dolomite
rhombs by gypsum.
Replacement and dissolution
of dolomite crystals began
from the cores and expanded
outward.
SEM image of hollow dolomite crystal showing
etched crystal interior, Cayman Formation
(Miocene), Grand Cayman. Image width 70 μm.
James & Jones, 2015

10. Dolomite Petrography
• Dedolomite:
Thin-section images (PPL and
stained with Alizarin red S) of
Oligocene Limestone, Southern
Australia.
• (A) Numerous dolomite crystals that
have been dissolved and their
hollow cores are the site of later
calcite precipitation (red). Image
width 1.4 mm.
• (B) Close-up of a single crystal,
image width 200 μm.
James & Jones, 2015