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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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<blockquote data-quote="user 4386" data-source="post: 652128" data-attributes="member: 4386"><p>I should clarify - karats simply tell you whether a set amount of silver and copper are analysed with the gold - so there are only a few possible numbers and any if them have gold, alloyed purposely to a specific composition by a jewller/metallurgist. All of them have gold - strictly it is meaningless to say that a sample has x karat gold, y karat gold and z karat gold because it can only be one of these. . What you want is usually g/t (grams per tonne) or ppm (parts per million) of gold, which is a sliding continuous scale and gives one unique answer - the amount of gold present in the sample. So a gold ring will be manufactured to 9. 12 or 24 karat (only one of these for one ring) - the lower the karats the less expensive the ring. It is a measure of the other metals alloyed with the gold - intentionally, in a specific ratio. Also, yellowness of gold is not a reliable indicator because copper can increase the shade of yellow in a ring with less gold - the hallmark stamped on the ring is its certified number of karats (same for any other gold jewellery). .</p><p></p><p>Fire assay is most accurate as long as you have an adequate sample size, although I often use a cheaper method (usually something like AAS) if I just want an approximate value (i.e. to know significant gold is present). However the error can be 30% in that case (I once ran a series of samples, each by both methods, and that was the error I found). The cheaper method is more of a problem if a lot of some sulphide mineral(s) is present - it is more accurate where you are dealing with less than a couple of percent sulphides in white quartz and where the gold is free, not locked up inside the sulphide minerals.</p><p></p><p>I am mentioning this for others as well - many people use the wrong assay method or the wrong sized sample for the material they are assaying.</p><p></p><p>[URL unfurl="true"]https://www.onecklace.com/tips/karat-gold-understanding-gold-purity/[/URL]</p></blockquote><p></p>
[QUOTE="user 4386, post: 652128, member: 4386"] I should clarify - karats simply tell you whether a set amount of silver and copper are analysed with the gold - so there are only a few possible numbers and any if them have gold, alloyed purposely to a specific composition by a jewller/metallurgist. All of them have gold - strictly it is meaningless to say that a sample has x karat gold, y karat gold and z karat gold because it can only be one of these. . What you want is usually g/t (grams per tonne) or ppm (parts per million) of gold, which is a sliding continuous scale and gives one unique answer - the amount of gold present in the sample. So a gold ring will be manufactured to 9. 12 or 24 karat (only one of these for one ring) - the lower the karats the less expensive the ring. It is a measure of the other metals alloyed with the gold - intentionally, in a specific ratio. Also, yellowness of gold is not a reliable indicator because copper can increase the shade of yellow in a ring with less gold - the hallmark stamped on the ring is its certified number of karats (same for any other gold jewellery). . Fire assay is most accurate as long as you have an adequate sample size, although I often use a cheaper method (usually something like AAS) if I just want an approximate value (i.e. to know significant gold is present). However the error can be 30% in that case (I once ran a series of samples, each by both methods, and that was the error I found). The cheaper method is more of a problem if a lot of some sulphide mineral(s) is present - it is more accurate where you are dealing with less than a couple of percent sulphides in white quartz and where the gold is free, not locked up inside the sulphide minerals. I am mentioning this for others as well - many people use the wrong assay method or the wrong sized sample for the material they are assaying. [URL unfurl="true"]https://www.onecklace.com/tips/karat-gold-understanding-gold-purity/[/URL] [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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