Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Iwonda on 04/04/2021 04:20:21
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Under certain conditions minerals can morph into something different than what they started out as. Can a mineral such as jasper which is mostly silicon be forced to morph into something that is mostly calcium?
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Rocks can be changed chemically by metasomatism. As to whether the silicon atoms in jasper can be largely replaced by calcium atoms, I don't know. I would lean towards no, as silica isn't very soluble in water. If you were talking about more soluble species, like magnesium, I'd say that would be more likely. I'm open to being corrected on this, however, as I haven't done a particularly large amount of research in this area.
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Minerals can be changed by heat and pressure to have different properties, even though they retain the same atoms.
- The pressures found on Earth (or in the center of the Sun) will not change Silicon atoms into Calcium atoms.
Minerals can be changed by being dissolved and being replaced by other minerals.
- Deposits of Calcium Carbonate (eg from coral, shells or bones) can be dissolved in acidic conditions, and replaced by other minerals
- At Lightning Ridge, Calcium Carbonate fossils have been replaced by opal (Silicon Dioxide)
See: https://australian.museum/learn/australia-over-time/fossils/sites/lightning-ridge/
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Silicon atoms will not change into calcium atoms.
It is possible for silicon atoms to be replaced by calcium atoms to some extent, but I think it would be very difficult because they have very different chemistries, and thus play very different roles in their minerals.
Calcium exists in minerals as an ion with a 2+ charge. ie Ca2+
Silicon primarily exists in minerals tightly bonded with oxygen atoms and forming negatively charged ions known as silicates. (there are many, many, many different types of silicates depending on how many silicon atoms are contained, and whether they form open chains or rings, or polycyclic systems...
In short, it would be very hard to swap out something like SiO44– for Ca2+ because neither the sizes nor the charges match.
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Thanks for all the great replies and I do agree with them all. The reason I asked that question is because I found a stone that no scientist can ID and or explain. It appears to have started out as an orange mineral like jasper but was in an environment that morphed it into like five different minerals and one of those minerals is calcium. It also changed it crystal structure and color, part of it is opaque, some translucent and some transparent. I have contacted several geologist at major universities and museums all across the country and I am told that they can not ID or explain what this is. As of now the stone is classified as an unknown.
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I have contacted several geologist at major universities and museums all across the country and I am told that they can not ID or explain what this is. As of now the stone is classified as an unknown.
I suspect that the lack of identification is more likely due to lack of interest or lack of access to the sample than a highly mysterious new mineral. Did you just email them pictures and not receive any responses? Or has it been examined, and left the experts puzzled?
It appears to have started out as an orange mineral like jasper but was in an environment that morphed it into like five different minerals and one of those minerals is calcium.
Is it possible that it is a concretion or co-deposition of many things, rather than one turning into many? Also, calcium is not a mineral, it is an element, and is not found in nature in its elemental form. Common calcium-containing minerals include aragonite, apatite, calcite, fluorite, gypsum... which do you mean?
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I thought for sure that it was some sort of concretion but that hasn't been confirmed nor denied. All of the geologist that have looked at this stone in hand has told me that they do not know what it is nor can they explain how it got to be the way it is. I was told I needed to take it to a university and see if they could shed some light on this stone. Took it to a university and was told the same, they had no ideal as to what this stone is or how it got to be tis way, was told that an in depth exam would most likely be very costly and take a good deal of time. Tried to get an appraisal so that I could maybe place it in a museum but was told by an appraiser that a dollar amount could not be assigned to the stone because they weren't aware of anything to compare it to.
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You can probe the sample with a laser, electrons or protons, to get an idea of the chemical composition.
- Most rocks are made up of many small crystals, with different chemical composition
- It's best to probe individual crystals separately
This would be expensive, unless you are a student with "free" access to such an instrument at university.
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I've had an edx analysis done on different areas which does show that the composition changes. I would love to get an xrf analysis done to see what it detects but I'm no student and these scans are very costly. It's not just the composition that changes throughout this stone, it also changes it's hardness, luster and it's crystal structure. Part of it is opaque, translucent and transparent. One end starts out looking like a piece of compressed wrinkled orange jasper with the opposite end looking like a piece of wrinkled chocolate bar. I have searched all over the web and can not find a chocolate stone/gem that looks like that, really cool.