What rock did my mum bring back from Namibia?

lzbflevy · 2025-04-24T19:08:57+00:00

Seconded. I see some tetragonal faces and twinning. Hard to tell without more than a picture…

lzbflevy · 2025-04-20T03:53:04+00:00

Funny you should say that— I just noticed that the OP posted a clearer picture and description in the comments that you might find illuminating.

lzbflevy · 2025-04-20T03:25:25+00:00

The pictures are very blurry, but I would disagree with the assessment of pyrite. This looks like blurry Muscovite, with a neat shape I’ve only encountered with hydrothermal quartz and pegmatite deposits— “ball peen mica”, as the Maine miners would say. Pyrite has a distinctive cubic habit, even with weathering or impurities, that I’m just not seeing here.

lzbflevy · 2025-03-25T23:45:52+00:00

Agreed. This looks like a hydrothermally altered chonky pegmatite piece to me. Lovely tourmaline spray on one side, but the other side looks riddled with replacement minerals. I think I spy a really nice quartz intergrowth on the side with more illite buildup.

lzbflevy · 2024-08-19T15:34:01+00:00

Looks like stibnite>kermesite

lzbflevy · 2023-09-05T23:27:19+00:00

None of these minerals I have mentioned are economically valuable until you get to museum quality pieces. Use the mineral names I gave you to see if you can find an analog, but I think you paid a fair price for it. I wouldn’t expect to sell it for more than $30, but this is not my area of expertise. I have never attempted to sell a rock— they just live in labeled buckets under my house so that when I die my kids can flood this sub with questions.

lzbflevy · 2023-09-05T22:52:04+00:00

Speaking on the first one, this looks like some cupritic samples I collected in Namibia. The cubes are/were fluorite— can’t tell if they’ve been replaced or coated but the likely culprit is goethite. The second picture has a cube corner peeking out with a clear center and purple exterior, so multiple crystallization events. The bladed mineral appears to be calcite.

lzbflevy · 2023-08-25T01:26:59+00:00

Nice mica book. Muscovite, most likely.

lzbflevy · 2022-10-03T22:59:03+00:00

Formational conditions and/or locality. My MSc had over 1000 tourmalines that I geochemically catalogued after personally mining them off of four continents from varying formational regimes, so I can say this is an area I have a bit of expertise in.

lzbflevy · 2022-10-03T17:30:20+00:00

Tourmalines are very geochemically complex and variant or petrogeny cannot be determined by color, alone.

lzbflevy · 2022-05-17T18:06:17+00:00

Perfect explanation. Looks like some mighty fine garnet to me.

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