Ad
related to: minerals in thin section
Search results
Results From The WOW.Com Content Network
Thin sections are prepared in order to investigate the optical properties of the minerals in the rock. This work is a part of petrology and helps to reveal the origin and evolution of the parent rock. A photograph of a rock in thin section is often referred to as a photomicrograph.
With a known thickness of the thin section, minerals have specific and predictable colours in cross-polarized light, and this chart can help identify minerals. The colours are produced by the difference in speed in the fast and slow rays, also known as birefringence.
Such crystal orientations are findable in thin section by looking for slices through minerals which are not isotropic but that nevertheless appear uniformly black or very dark grey under normal cross-polarised light at all stage angles (i.e., are "extinct").
Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include:
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. Isotropic minerals, opaque (metallic) minerals, and amorphous materials (glass) do not allow light transmission under cross-polarized light (i.e. constant ...
Photomicrograph of a thin section of gabbro in cross-polarized light. A petrographic microscope is a type of optical microscope used to identify rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks.
Photomicrographs of a thin section containing an amphibole crystal; under cross-polarized light on the left, and plane-polarized light on the right. Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. [4] In chemical composition and general characteristics they are similar to the pyroxenes. The chief differences from ...
Optical relief (usually noted as simply relief) is a visually observable property in optical mineralogy used to identify minerals based on their refractive index.Relief is determined by observing the degree to which grains stand out from a mounting medium of known refractive index, [1] usually either oil or Canada Balsam.