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Identity HelpElemental sulfur on magnetite?

5th Dec 2016 12:15 UTCJyrki Autio Expert

This is from Hangaslampi deposit, Kuusamo, Finland.
Hangaslampi

The EDS is from 0.1-0.5 mm yellow crystals. Are there other options? Some organic compound?

I suppose these are formed by a biological process. They are mainly found from spaces left from dissolved calcite or dolomite. What kind of biology can produce elemental sulfur, if it is it?

Cheers

Jyrki

5th Dec 2016 13:28 UTCReiner Mielke Expert

I see two yellowish things, small balls and prismatic crystals. I am assuming you analyzed the balls? The only things Kerry cannot detect is elements lighter than Na but I cannot think of anything that is not water soluble that could be combined with sulphur and look like that. Sulfur is slowly soluble in toluene you could test it with that. Also it has a very low melting point so you could test it with a hot needle to confirm.

5th Dec 2016 13:45 UTCJyrki Autio Expert

Slightly elongated and rounded yellow ones were analyzed. In this sample there are also many zeolite looking prismatic white crystals. I have no idea what the bigger orange one is at this point.

No toluene at hand but the yellow ones are not water soluble. There is actually quite much of this finegrained yellow sand in the quarry separated, carried and deposited by the rain water.

5th Dec 2016 14:11 UTCPavel Kartashov Manager

Usual benzine also dissolves sulphur well.

Can't it to be some component of explosive?

5th Dec 2016 14:17 UTCJyrki Autio Expert

Pavel- I believe it can be used for that. Good idea.

5th Dec 2016 14:26 UTCJyrki Autio Expert

Seriously, I'm quite sure this sample is from inside of larger sample I trimmed. Not from an exposed surface material.

5th Dec 2016 15:51 UTCGregg Little 🌟

Jyrki; You said, "They are mainly found from spaces left from dissolved calcite or dolomite."

Did you dissolve the carbonate out? If so what acid did you use? Could this be a reaction product or another mineral exposed after dissolving the carbonate?

5th Dec 2016 16:31 UTCJyrki Autio Expert

Good questions. I see I need to be more accurate.

I did not dissolve anything. These are found from small voids left from naturally dissolved mineral which could have been calcite or dolomite.

These are found in place I did not observe any use of explosives. Only the moraine cover was removed to expose bedrock.

These were only observed in places of massive magnetite outcrops, several m2 in area.

5th Dec 2016 16:42 UTCReiner Mielke Expert

Certainly is a most unusual association something I would never expect. Looks like I will have to take a closer look at any massive magnetite I find from now on.

5th Dec 2016 17:44 UTCGregg Little 🌟

As Reiner says this does look very unusual so what you might try to figure out first is whether this is a mineral as part of the depositional genesis with the magnetite revealed by the carbonate removal, or a surface alteration product after ground waters dissolved the carbonate and precipitated this unknown in the void space.

While prospecting in the Yukon I came across a fracture filled with an Epsom salt like mixture, probably a mixture of hydrated magnesium sulphates. Although northern Canada is cold, it is also relatively arid so, not all that surprising. I encountered surface mineralization in southern BC where gypsum (tiny ones of the rams horn habit) was growing on the surfaces inside a mine audit entrance. Another surface mineralization I have heard of are romerite and copiapite in the Spences Bridge area, BC.

Ground water acting at the till-bedrock contact could produce some interesting precipitates depending on the deposit's mineralogy.

5th Dec 2016 18:15 UTCFranz Bernhard Expert

Very interesting!

What is the brownish grain in the upper right corner?

Maybe there were sulphides present in the S-filled vugs? Perhaps sphalerit?

The metal is gone, the S^2-- was only partly oxidized and some was left behind as elemental S?

Not an unusual phenomenon.

Franz Bernhard

6th Dec 2016 02:54 UTCAlfredo Petrov Manager

Sulfur is not rare as a secondary product where pyrite has decomposed, leaving a vug partially filled with loose granular native sulphur. I've seen this a few times in California gold mines. Surprisingly, no iron oxides are left in those vugs, so the iron was completely leached out. So I suspect Jyrki's rock was originally an intergrowth of magnetite and pyrite.

6th Dec 2016 06:27 UTCChristian Auer 🌟 Expert

The luster of the yellow xtls remind me on sulphur. Very typical! The white could be another sulphate.

6th Dec 2016 12:44 UTCJyrki Autio Expert

Thank you for many answers.

After a little test it is obvious It burns and smells like sulfur. Freshly opened vugs seem to be half full of uniformly sized granular sulfur and when excess is poured out, what is left looks like picture in first post.

I still think the vugs are after some soluble mineral other than pyrite because there are a lot of quite unaltered pyrite cubes in magnetite and these vugs are irregular in shape.

Seems like a good subject to read more and also try to find out what the white and brown crystals are.

9th Dec 2016 16:54 UTCUwe Kolitsch Manager

I agree with Franz.

11th Dec 2016 12:04 UTCJoel Dyer

Jyrki, I scoped the samples of this that you sent to me.

It looks almost as if elongated crystals are partly frozen in "congeled" yellowish sulphur(?). There also seem to be both elongated (monoclinic??) whitish and more grain like or rounded rectangular whitish crystals. Also found a very few more reddish or pinkish crystals. So there might be 2-3 different sulphate(?) minerals involved?

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