Thin section

petrographic thin sectionpolished sectionsectionsectioningthin sectioningthin sectionsthin-sectionedthin-sections
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.wikipedia
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Optical mineralogy

opticalmicroscopic petrographyoptical properties
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.
Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope.

Petrography

petrographicpetrographerpetrographically
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.
The detailed analysis of minerals by optical mineralogy in thin section and the micro-texture and structure are critical to understanding the origin of the rock.

Microscope slide

cover slipslidemicroscopic slide
It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick.
A range of other sizes are available for various special purposes, such as 75 x 50 mm for geological use, 46 x 27 mm for petrographic studies, and 48 x 28 mm for thin sections.

Petrographic microscope

polarizing microscopeoptical microscopypetrographic polarizing light microscope
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Mineral

mineralsmineral depositsaccessory mineral
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.
When a mineral is sufficiently thin (e.g., in a thin section for petrography), it may become transparent even if that property is not seen in a hand sample.

Plagioclase

plagioclase feldsparcleavelanditesodic plagioclase
Plagioclase for example can be seen in the photo on the right as a clear mineral with multiple parallel twinning planes.
The composition of a plagioclase feldspar is typically denoted by its overall fraction of anorthite (%An) or albite (%Ab), and readily determined by measuring the plagioclase crystal's refractive index in crushed grain mounts, or its extinction angle in thin section under a polarizing microscope.

Undulose extinction

undulatoryundulose
The extinction in waves is called undulose extinction and indicates dislocation walls in mineral grains.
Undulose extinction or undulatory extinction is a geological term referring to the type of extinction that occurs in certain minerals when examined in thin section under cross polarized light.

Extinction (optical mineralogy)

extinctionExtinction angleextinction position
They change the crystallographic orientation across the walls, so for example in quartz, the two sides of the wall will have slightly different extinction angles and thus result in undulose extinction.
Extinction is a term used in optical mineralogy and petrology, which describes when cross-polarized light dims, as viewed through a thin section of a mineral in a petrographic microscope.

Igneous rock

igneousigneous rocksdecompression melting
Those grains that are monocrystalline quartz are more likely to have been formed by igneous processes.
Generally, the mineral constituents of fine-grained extrusive igneous rocks can only be determined by examination of thin sections of the rock under a microscope, so only an approximate classification can usually be made in the field.

Rock microstructure

texturetexturaltextures
This technique has been used to study the microstructure of fine-grained carbonates such as the Lochseitenkalk mylonite in which the matrix grains are less than 5 μm in size.
This information can usually be seen best under a binocular microscope, not in a thin section.

Conoscopic interference pattern

interference figure2Voptic sign
However, for certainty, other distinguishing features of quartz include the fact that it is uniaxial, it has a positive optic sign, length-slow sign of elongation, and zero degree extinction angle.
The thin section containing the mineral to be investigated is placed on the microscope stage, above one linear polariser, but with a second (the "analyser") between the objective lens and the eyepiece.

Sandstone

sandstonesred sandstoneSandstein
Some note the trend for immature sandstones to have less polycrystalline quartz grains compared to mature sandstones, which have grains that have passed through many sedimentary cycles.
Sandstone classifications are typically done by point-counting a thin section using a method like the Gazzi-Dickinson Method.

Ceramography

ceramic microstructureCeramic petrographyceramics
* Ceramography: thin sections of ceramics
Alternatively, non-cubic ceramics can be prepared as thin sections, also known as petrography, for examination by polarized transmitted light microscopy.

Canada balsam

balsamCanadian balsam
An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on.

Laboratory

laboratorieslaboratory equipmentlab
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Rock (geology)

stonerockrocks
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Soil

soilsdirtsoil moisture
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Polarization (waves)

polarizationpolarizedpolarized light
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Electron microscope

electron microscopyelectron microscopeselectron
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Electron microprobe

electron probe microanalysisElemental MappingEPMA
In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe.

Diamond blade

diamond sawdiamond saw bladesdiamond blade saw
A thin sliver of rock is cut from the sample with a diamond saw and ground optically flat.

Micrometre

μmµmmicrometers
It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick. This technique has been used to study the microstructure of fine-grained carbonates such as the Lochseitenkalk mylonite in which the matrix grains are less than 5 μm in size. An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on.

Crystal twinning

twinningtwinnedtwins
Plagioclase for example can be seen in the photo on the right as a clear mineral with multiple parallel twinning planes.

Pyroxene

clinopyroxeneorthopyroxenepyroxenes
The large blue-green minerals are clinopyroxene with some exsolution of orthopyroxene.

Petrology

petrologistpetrologicalpetrologic
This work is a part of petrology and helps to reveal the origin and evolution of the parent rock.