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Earth and Space Sciences · 术语表

什么是 Thin section; polarising microscope？

又称： thin section · polarising microscope

Definition 16.11 High School Earth and Space Sciences · 第 16 章 — Minerals

A thin section is a slice of rock ground down to a thickness of $0.03\,\mathrm{mm}$ and mounted on a glass slide: at this thickness light passes through most minerals. A polarising microscope is a microscope fitted with two polarising filters, one below the slide and one above it. The section is seen in plane-polarised light with the lower filter only, and between crossed polars when the upper filter is added with its direction perpendicular to that of the lower one.

Left and centre: the same basalt in thin section, in plane-polarised light and between crossed polars. The rock is fine grained: small elongated crystals, mostly plagioclase, and black specks that let no light through in either view; between crossed polars the crystals light up in greys and colours. Photographs Chmee2 (CC BY-SA 3.0). Right: crystals of quartz in a granite, between crossed polars, each in its own shade of grey (the scale bar is 0.5\, mm). Photograph Michael C. Rygel (CC BY-SA 3.0). — Left and centre: the same basalt in thin section, in plane-polarised light and between crossed polars. The rock is fine grained: small elongated crystals, mostly plagioclase, and black specks that let no light through in either view; between crossed polars the crystals light up in greys and colours. Photographs Chmee2 (CC BY-SA 3.0). Right: crystals of quartz in a granite, between crossed polars, each in its own shade of grey (the scale bar is $0.5\,\mathrm{mm}$ ). Photograph Michael C. Rygel (CC BY-SA 3.0).

Left and centre: the same basalt in thin section, in plane-polarised light and between crossed polars. The rock is fine grained: small elongated crystals, mostly plagioclase, and black specks that let no light through in either view; between crossed polars the crystals light up in greys and colours. Photographs Chmee2 (CC BY-SA 3.0). Right: crystals of quartz in a granite, between crossed polars, each in its own shade of grey (the scale bar is 0.5\, mm). Photograph Michael C. Rygel (CC BY-SA 3.0). — Left and centre: the same basalt in thin section, in plane-polarised light and between crossed polars. The rock is fine grained: small elongated crystals, mostly plagioclase, and black specks that let no light through in either view; between crossed polars the crystals light up in greys and colours. Photographs Chmee2 (CC BY-SA 3.0). Right: crystals of quartz in a granite, between crossed polars, each in its own shade of grey (the scale bar is $0.5\,\mathrm{mm}$ ). Photograph Michael C. Rygel (CC BY-SA 3.0).

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