Petrographic section, Hillhouse gabbro
Introduction
The photograph on this page of Petrographic section, Hillhouse gabbro by Jonathan Wilkins as part of the Geograph project.
The Geograph project started in 2005 with the aim of publishing, organising and preserving representative images for every square kilometre of Great Britain, Ireland and the Isle of Man.
There are currently over 7.5m images from over 14,400 individuals and you can help contribute to the project by visiting https://www.geograph.org.uk
Petrographic section, Hillhouse gabbro
Image: © Jonathan Wilkins Taken: 29 Aug 2018
A photomicrograph of a petrographic section of the local rock, an analcime gabbro of Carboniferous age. The rock slice has been cut and lapped to 30 micrometres thickness, then photographed by a high-resolution camera attached to a polarising microscope. The false colours are caused by retardation of the polarised light which travels at different speed depending upon its alignment with the crystal axes. Perfectly isotropic materials are completely black, as are crystals whose axes align with the planes of polarisation. The colours enable geologists to identify the minerals of the rock - here pyroxene and olivine are bright, while plagioclase feldspar is humbug-striped. The length of the large, blue crystal is around 1.6mm. The section was prepared by the contributor in his own workshop/kitchen from material collected from Hillhouse Quarry. See: Image] for location.
Images are licensed for reuse under creativecommons.org/licenses/by-sa/2.0
Image Location
Latitude
55.573965
Longitude
-4.615201