It looks volcanic in origin and I speculate that it probably contains iron. Best described as a thin layer of bubbly chocolate on a thin base of conglomerate rock that appears to have been once molten. Dark brown bubbles (almost perfect hemispheres) locked together, showing various diameters up to 5mm, height up to 2mm, quite hard, although a stainless steel knife will mark it, with a dull to very slight lustre and a very smooth texture. The undersurface of the bubbles is a dull orange/yellow, appearing earthy and powdery, but is actually brittle. It was found in the side of a low cliff near the shoreline in an area described as 'tertiary basalt' on a geological map.
I've had it for several years now and my curiosity is peaking. Any help towards pinning it down would be much appreciated.
2006-11-18
22:17:15
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1 answers
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asked by
falzoon
7