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PhotosPumpung Lukaas mine, Cempaka diamond fields, Riam Kanan, South Kalimantan Province, Kalimantan, Indonesia

4th Jul 2019 09:07 BSTUwe Kolitsch Manager

Jason Utas suggested that these are tectites (indochinites).

I thought it would be pieces of the limonite-rich, water-worn gravel hosting the diamonds (note: photo wasn't made by me).

Any opinions?

4th Jul 2019 10:06 BSTJolyon Ralph Founder

Look more like tectites than limonite to me. I wonder if the title is incorrect and these are just tectites offered for sale

4th Jul 2019 11:53 BSTKeith Compton Manager

An article: van Leeuwan, T.M. (2014) The enigmatic Sundaland diamonds. Proceedings of Sundaland Resources 2014 MGEI Annual Convention Conference Paper, discusses the diamonds from Cempaka.

One paragraph states: "The Kalimantan diamonds are commonly found together with a mineral suite that includes corundum, diaspore, zircon, chromite/spinel, pleonaste, rutile, and rare tektite (Ubaghs, 1941)"

The Ubaghs reference is: Ubaghs, J.C.H. 1941. Diamonds in Borneo. Report held in Perpustakan Direktorat Geologi, No F 41-2 (Translated from Dutch).

So perhaps they are tektites


4th Jul 2019 14:43 BSTUwe Kolitsch Manager

Thanks, Keith - very interesting.

5th Jul 2019 07:07 BSTUwe Kolitsch Manager

My colleague and meteorite/tectite specialist, Ludovic Ferrière, thinks the two on the right side are tectites, but he is not sure about the piece on the left.

12th Jul 2019 00:25 BSTJason Utas

The specimen on the left is also a tektite. The large ~flat face with the single pit in it is an old break that exposed a bubble and has since been partly re-etched by groundwater. Faint flow-banding / schlieren are visible on the left side of the flat surface.

I looked around on Google for a similar tektite; this piece of Darwin glass is somewhat similar, although Darwin glass is generally much more vesicular than indochinites, excluding the Muong Nong layered tektites...

12th Jul 2019 11:21 BSTUwe Kolitsch Manager

Ok, caption fixed.
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