Ocean Jasper #3

Ocean Jasper from Madagascar. Close up of one spherule in the fine-grained silica matrix.... more

by - MicROCKScopica -

Title

Ocean Jasper #3

Artist

- MicROCKScopica -

Medium

Photograph - Photomicrograph

Description

Ocean Jasper from Madagascar. Close up of one "spherule" in the fine-grained silica matrix.
"There was a penetration of the light into solid substance so that I seemed to see into things, deep in...".
John Steinbeck was not thinking of rocks when he wrote this sentence in "Travels with Charley - In search of America". However, his feeling exactly reflects what people should think when looking at rock photomicrographs such as in this reportage on "Ocean Jasper".
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This is a variety of jasper found only in Madagascar. Being mined out, Ocean Jasper is becoming among the most collectible stones for lapidary. Ocean jasper is characterized by the presence of small spherical aggregates (spherulites or "orbs"), just a few mm in diameter, that derive from a process of alteration and silicification of former volcanic flows of tuffs or rhyolites. I have long been searching for affordable samples of Ocean Jasper, until I saw a necklace in a market stall. I cut all the beads, prepared thin sections from them, and put them under the microscope: they turned out to contain a microscopic garden of flowers of quartz in a fine-grained silica matrix. In places some coarser crystals form "rosettes" in a lawn of fibrous quartz. Spherulites are among the most interesting subjects I have worked with: they can be single or in clusters, made of fibrous or crystalline silica, with or without opaque-rich cores. These images demonstrate how variegated and exciting rocks can be, when observed from within.
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All images are transmitted, polarized light photomicrographs of 30-micron-thick rock slices (geological "thin sections"), with width of view ranging from 1 to 5 mm. Images were taken with a Canon EOS 550D camera mounted on the trinocular head of a Zeiss Axioscop 40 Pol microscope.

Rock cut, sliced and thinned down to a regular thin section (30-micron thickness)
Technique: Photomicrograph under polarized light, crossed polars plus red tint plate

Uploaded

May 10th, 2013