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EducationHematite on Malachite

31st Dec 2017 01:17 UTCDennis Curtis

Last pressing question:

These are Hematite on Malachite from Sepon Mine, Vilabouly Dist., Savannakhet Prov., Laos.

I have three specimens. I haven't seen any others. Has anyone here seen this and has this type been found in any other mines?

I collect unique copper specimens and don't know a lot about petrology yet. I do know that Tsumeb is copper heaven!

The Malachite has an intense metallic sheen better than the pictures show.

I would be grateful for more info on these specimens.

19th Apr 2018 22:31 UTCGregg Little 🌟

Hi Dennis;

This sample occurs in the oxide alteration zone of the Sepon Basin gold-copper deposit(s). The primary mineralization is finely disseminated gold and copper sulphides along with pyrite and arsenopyrite in sedimentary rock. Associated with igneous intrusive activity and faulting focused the mineralization in the Sepon mineral district. This name applies to the area around the Sepon Mine that exhibits similar geology and ore genesis characteristics.

Upon erosion, and the introduction of water and oxygen, the sulphides in the upper (near surface) zone were oxidized forming copper and iron secondaries (malachite and hematite in your case) and this is the probable source of your specimen. Although a somewhat technical article (see link below) you might find parts interesting describing the "home" of your specimen. There is also a local history of the deposit's discovery. There is also references to the giant low grade gold deposits of the USA (Carlin type).

http://library.dmr.go.th/Document/DMR_Technical_Reports/2013/36782.pdf

Although not a unique mineral assemblage, it certainly is aesthetically pleasing.

3rd Jun 2018 22:48 UTCDennis Curtis

Thank you so much Gregg!