Crossed polarised filter microscopic views of Norite thin section from Huntly Aberdeenshire

Norite, also known as orthopyroxene gabbro, is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. Norite may be essentially indistinguishable from gabbro without thin section study under the petrographic microscope. The principal difference between norite and gabbro, however, is the type of pyroxene of which it is composed; norite is predominately composed of orthopyroxenes, largely high magnesian enstatite or an iron bearing intermediate hypersthene, whereas the principal pyroxenes in gabbro are clinopyroxenes, generally medially iron-rich augites (https://en.wikipedia.org/wiki/Norite).

The following are views under the Zeiss IM microscope using 4x and 20x objectives and Bresser MikrOkular camera – and my homemade linear polarised filter arrangement that allows me to view using cross polarisation.

Andy

Norite-Huntly-Aberdeenshire-slide-marked-A13-x4-objective-cross-polars-Zeiss-IM-090717.bmp (below):

To show the detail of the crystal structure in the sample above, I photographed multiple fields using x20 objective and used Microsoft’s Image Composite Editor to stitch them together into a panorama – to see the detail you will need to click on the photo to load it into separate window:

Following are individual panes that made up the above image:

 

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