Deskripsi Sedimen Petrografi
Deskripsi Sedimen Petrografi
Deskripsi Sedimen Petrografi
uk/~oesis/micro/
Sandstone
This sandstone is made of quite well rounded grains of quartz, cemented
together by calcium carbonate. Cambrian, NW Scotland.
Field of view 3.5 mm, polarising filters.
Greensand
The green colour that this Cretaceous sandstone has in hand specimen comes
from the rounded grains of the mineral glauconite, seen here among quartz
grains in a matrix of clay and calcium carbonate. Field of view 3.5 mm.
Limestone (oolitic)
Oolitic limestone is made up largely of sand-sized, rounded pellets of calcium
carbonate, which are formed in warm shallow water where carbonate sediment
is moved about by currents. Isle of Skye, Scotland. Field of view 4.5 mm,
polarising filters.
Limestone (oolitic)
Oolitic limestone is made up largely of sand-sized, rounded pellets of calcium
carbonate. In this closer view we can see that some of the pellets have grown
by adding layers of calcium carbonate onto a tiny sedimentary grain of quartz.
Isle of Skye, Scotland. Field of view 3 mm.
Limestone (dolomitic)
In this limestone, diamond-shaped crystals of dolomite (calcium magnesium
carbonate) have grown after deposition, while the sediment was being changed
into rock. They replace the fine calcium carbonate mud (dark material in the
photo) that makes up the rest of the rock. Field of view 3.5 mm.
Coal
Coal is mostly opaque under the microscope, as you might expect. The red-
black material (vitrinite) in the thin section is the part of the coal that appears
shiny black in hand sample, and is made from compressed wood tissue. The
loop-shaped orange-yellow objects are the flattened large spores of plants.
Field of view 3 mm.