|MadSci Network: Science History|
Whee - This is a jewel of a question (so to speak). As to Who came up with the karat (or carat) system or exactly When, I fear this is lost in the murky past. However, as to Where, I can point you in the right direction. I fear my ancient history is lacking so I can only tell you this was already going on MORE than 3000 years ago. (There are spectacular ruined cities in the Indian jungles that are older than that... but I digress) But anyway, when I say the When and Who are lost in the murky past I mean the Ancient Past. While Western europeans were still drawing on animal skins with burnt sticks the Persians and Chinese and other parts of the Asian, Indo-European and Near Eastern world had already adopted standardized measurment. When it came to precious metals and gems, the standard had to be small and reliable. Carob seeds became the standard, and one standard unit of gold was 24 of the carob seeds. The word karat (and carat, the unit of weight used to measure gems) derives from the; Italian "carato", the Arab "qirat", or the Greek "keration", all meaning the fruit of the carob tree. Now, we all agree that 24 karat is pure gold, or 24 parts gold. So 18K is 18/24 gold and 14K is 14/24 parts gold. Incidentally 10K is the lowest that can be sold as "gold" in the US, though things can also be "gold plated" or even "electroplated" (more chem... ). Some countries set the threshold higher (14K or 18K) and a few as low as 8K or 9K. So what are the other parts? Well it depends on what one wants. You can make different color alloys; Yellow gold - usually copper and zinc alloy Red or Rose gold - more copper and less zinc White gold - this one has many ingredients and can therefore vary widely in price, quality and durability. First, please nothe that sometimes Pt (platinum) is called "while gold." However gold in a white alloy is mixed with avariety of things including: zinc, copper (far less than in yellow or red gold), nickel and/or platinum. Green gold - copper and silver Blue gold - iron The metric craze has also hit the world of fine jewelry, so many european markets prefer to work using a "fineness" scale based on a) a decimal version of the karat component and b) parts of 1000. 24K gold or 100% gold has a fineness of 999 18K gold or 75% gold has a fineness of 750 and 14K gold or 58.3% gold has a fineness of 585 and so on.. As to where can you find more? General advice. Look under headings such as Gemology, Precious Metals, and of course Gold in a library index. More specifically: here are a bunch of jewelry and prospecting sites I used to research this. Many of them have links I didn't need to use, but they may be of interest to you. Beyond these sites, you may want to find a gregarious independant jeweler who does his/her own work, or find a university with a Gemology department and start nosing around. Happy Hunting! The sites: http://www.pineglen.com/g_facts.htm http://www.minerals.net/gemstone/gemstone/gold/gold.htm http://goldmuseum.home.mindspring.com/links.htm http://www.nettally.com/www/goodrocks/zinfo.html http://goldmaps.com/links.html
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