Lapidaryforum.net
Let's Rock => Prospecting => Topic started by: auscarver on October 24, 2022, 03:11:38 AM
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Last Christmas I found this deposit on my property, obicular jasper with magnatite and hematite.
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I have a friend that told me you don’t have poppie jasper without the white spots, yesterday I found this, it has more quartz in the mix, and hematite.
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Merry Christmas to you, eh? Still getting gifts from that deposit almost a year later. That's great.
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Very typical of west coast US poppy jaspers. If it was in situ what was the host rock? Here it is almost always from the mix of basalt lava and limestone or agrillite. I have seen contacts that were in situ and exposed in streams and they are spectacular.
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Thanks Vince and Frank. It is basalt lava like you said Frank. Also has a type of clorite. Clinoclorite, I had this green crystally material tested. It’s in contact with basalt. This lighter colour material is up above the darker base orange material, in situ but eroded more, any ideas why this material forms
the white dots but my other material doesn’t. More silica ?.
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Putting in my two pennies for Manganese. That pink...
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A bunch of research has been done recently on California poppy jaspers . The researcher says that the dots are remains of radiolarians usually ones that have had the outer shells broken off. He has used infrared spectroscopy and great visible light magnification to confirm. Ocean jasper is not radiolarians it is replaced rhyolite. There are fresh and saltwater
radiolarians and apparently your peanut wood is a mix of wood and freshwater radiolarian ooze.
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Great feedback. Radiolarians. So those little white dots in my piece pictured could be the remains of there silica shells. I may send some samples to get tested, I do have 3 rhodonite deposits close to this with heaps of manganese but it’s hematite causing the colour in this as that purple maroon stone has a reddish streak. A close up of some of the orbs in the dark base material. Shows it’s breciated also.
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More recent finds.
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Oolites make similar dots but have radial lines coming out from the center and typically have more layers ( shells) than radiolarians which have three or four if unbroken. the oolites form in soft sediment and seem to be chemical aggregation features.
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One recent paper I found proposes a theory that those orbs are not individual (giant) radiolarians, but clusters.
I still haven't seen any convincing evidence for this theory, it is really hard to analyze these structures with conclusive results. Thin sections, electron microscopy, perhaps Raman microscopy. Would be nice to see a good research paper dissecting poppy jaspers.
Whatever the origin may be, it really is a nice material! Have you tried cabbing or just polishing it yet?
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El Goog tells me Radiolarians formed symbiotic relationships with algae. The algal mat argillite I've been harvesting here in the Belt metaseds sometimes has chemical bleaching along microdikes that formed during deposition. The argillite is "red" with a high iron content and the bleached areas are the same dusty rose as your pale areas.
I'm assuming the oxidation along the feature (microfaulting, in this case) triggered a response in the organism to create a chemical scab of sorts and alter it's boundaries to cope with an opening. These mats acted like firm set jello. Fungi self heals and defends itself against other fungi by creating antimicrobial/fungal boundaries.
Possibly the white centers represent the chemical boundary between your Radiolarian aggregates and a fungal symbiont they are in the soup with
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Thanks for the great feedback, geology and gemmology is a great subject. I have polished a piece and have started a carving but not finished. It’s a tough stone without fracture, I do have a friend in New York that is a Dr of Geology, that may test this For me, see attached polished free form.
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Does the difficulty arise from grain orientation and differing fracture planes in the different minerals? I'm working with some porcelain-y contact zone meta-argillite that has clinochlore and pyroxene group minerals. One face behaves one way and the opposing face a contradictory fashion in terms of what's taking a high polish and what's staying dull.
It goes *tink tink* in a glassine way when I tap pieces together. Does yours sound like that? It's also tough as nails to cut/shape.
Are you in Australia? If so, and you didn't know, the Aus plate used to be congruent with the NA plate. Supercontinent Laurentia I believe. Makes sense it would be visually akin to West Coast NA poppies.
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The west coast poppy jaspers are all in terrains that came from central and south America but there is an earlier terrains that came from Borneo according to the included fossils.
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lithicbeads, would those be considered 'exotic terranes'?
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I live in the Tamworth region of NSW Australia, on an old fault area, peel fault, it runs through my property. Yesterday I found the best rough so far. Hard work very steep terrain, the brightest orange seems to come from the blocks that contain clorite as well as hematite.
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Another 2 pieces, I will carve one of these.
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Today I found what I think is specular hematite in my obicular jasper. A silvery gray metallic sheen. Chatoyant. My picture does no justice. Wish I could upload a video.
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In some areas here the entire matrix of the poppys is specular hematite in quartz.It is usually very difficult to photograph.
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Thanks Frank for your input. Does the Specular hematite show much chatoyancy in the material you have found. I have a piece that is very translucent and close to a cats eye, may be another mineral causing this as it’s a different colour to the specular. It’s in the mid bottom section of my picture.
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Phyllosilicates could be the culprit! Is the sheen (chatoyancy, asterism) metallic or sericitic/micaceous?
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Love the pics and Poppy Jasper really catches the attention. Slange :occasion14:
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In the Washington state poppy jaspers the chatoyantcy is from specular hematite.