Talk:Carat (purity)

If 18 carat gold is 75% gold, what is the other 25%?

Other metals, chosen for colour and hardness. Silver, Copper, Zinc and Nickel are often used. --W(t) 20:40, 15 February 2006 (UTC)

Platinum and Palladium are also used, but are not as common.

Qwertytrains (talk) 17:16, 14 February 2014 (UTC)

The Ottawa Mint in Canada is able to produce 99.999% pure gold compared with 99.99% pure gold which many other companies produce.

According to Timothy Green's book The World of Gold (written in the 60s, updated in the 70s) all gold from the USSR that turned up on international markets was "five nines" i.e., 0.99999 or 99.999% pure. South African gold was .996 even though it was stamped .995. By the way, you don't use the K when expressing it in decimal terms, and two of the five nines come before the decimal point if you're going by percentages.

As for the previous question, copper has, since ancient times, been added for hardness, but makes the gold look reddish. Look at a 22-K Krugerrand next to a .999 Canadian Maple Leaf, and you'll see what I mean. Since ancient times goldsmiths typically added silver to make it look more like pure gold, after adding a bunch of copper. (Krugerrands are just gold and copper). Then there's zinc, the magic ingredient. Zinc makes it possible to water down the gold to an extreme degree (with plenty of copper and silver) and still end up with an alloy that doesn't tarnish. I once had a ring stamped .333 (illegal in the USA). Zyxwv99 (talk) 19:39, 26 November 2011 (UTC)

I just looked it up (http://books.google.com/books?ei=CEzRTsL8CeiviQK_wMX5Cw&ct=result&id=uX1kAAAAIAAJ&dq=the+world+of+gold&q=purity#search_anchor) Turns out Russian gold was four nines, not five. Zyxwv99 (talk) 20:32, 26 November 2011 (UTC)

"Title 16: Commercial Practices PART 23—GUIDES FOR THE JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES"

I think this paragraph should be removed and replaced with a link or reference. To just have the whole excerpt from a legal document copy-pasted, especially if it's this voluminous, seems unacceptable. Or else, have the rest of the entry much more comprehensive (e.g. list the most common gold alloys etc.), so that this huge/bloated copy-pasted paragraph doesn't look too out of place. For instance, information like this one would be perfect for this article: http://www.utilisegold.com/jewellery_technology/colours/colour_alloys/ —Preceding unsigned comment added by 213.243.137.56 (talk) 13:18, 4 April 2009 (UTC)

Spelling - "carat" versus "karat".

Any views on this? It is my understanding that the "carat" form is used for mass, and the "karat" form for proportion. In any case, the use in this article is inconsistent.

• FYI*

Carat is a weight measurement used for gems. Karat is a measure of purity used for metals (most common is gold.) As far as the measure of purity is concerned the system is based upon a total of 24 parts i.e. 24K gold is pure gold, 18K is 18parts gold 6 parts other metals (which form an alloy) and so on.... 20:45, 18 September 2007 (UTC)

In the intro the article says: " In the United States and Canada, the spelling karat is now solely used for the measure of purity, while carat solely refers to the measure of mass weight" but this needs to be better phrased and the article spelling should be consistent with the title. --mervyn 12:30, 19 September 2007 (UTC)

Agree with Mervyn.

--Caesar J.B. Squitti: Son of Maryann Rosso and Arthur Natale Squitti (talk) 20:37, 8 October 2008 (UTC)

I've worked in the jewelry business for more than a decade now (one compared to my grandfather's eight) and I've never seen gold purity referred to as either 'carat' or ct. Those terms are used pretty exclusively in reference to gem stones, not precious metals. The karat is, and I would need to find some citation on this, an old apothecary's measure as precious metals are weighed by troy ounces which breaks down into 20 pennyweights or dwt. Now there is a difference between the stampings for gold manufactured in the U.S. and that manufactured in European countries. The American system uses the karat value while it's more common to see a decimal stamping such as .585 for 14k or .750 for 18k. Generally when a decimal stamping is used it's used to the thousandth point. The same is used for sterling silver with a 925 stamp that means the silver alloy contains 92.5% pure silver. Platinum is a little different as initially it was stamped as 10% Iridium meaning the alloy was 90% platinum. Contemporary platinum is usually stamped either 900 and 900PT to refer to Iridium platinum or 950 and 950PT to refer to Cobalt platinum which, naturally, is 95% platinum and 5% cobalt. But neither silver or platinum is given a karat value so while this info might be of tangential interest I don't know if it belongs in the article itself. Oh, and as I recall, gold below 10k doesn't have to bear a karat stamping even if it is stamped as gold. Usually you'll see it stamped at 'solid gold'. There's also the stamping for gold-filled items which usually is something along the lines of 1/20 12k gold filled meaning that 1/20th of the total pennyweight of the metal is a 12k gold exterior. (Cosmicomics (talk) 05:25, 6 March 2009 (UTC))

Apparently the United States Congress prefers "carat."

Gold Labeling Act of 1976 amending the National Gold and Silver Stamping Act of 1906 (U.S.C, Title 15, Chapter 8, Sections 294-300)

1976 - Pub. L. 94-450 substituted "three one-thousandth parts" for "one-half of one carat"

http://uscode.house.gov/download/pls/15C8.txt

(This part is about how much variance is allowed in the purity of the gold vs. the karat stamp. It used to be 1/2 k.) Zyxwv99 (talk) 21:11, 26 November 2011 (UTC)

Actually, that indicates that Congress no longer preferred using carat. Regardless, that does not indicate the current usage of carat. –Temporal User (Talk) 04:27, 1 December 2011 (UTC)

Correct. I should have said "preferred in 1906." Zyxwv99 (talk) 14:49, 1 December 2011 (UTC)

Volume

I removed the section below -- probably original research and not relevant since measure by volume is not used. --mervyn 12:45, 23 September 2007 (UTC)

What was removed is downright pedantic - has no bearing or usefullness to anyone in the real world. Gold is alloyed by weight in industry, and the rest is of minor curiousity to the writer, perhaps. In other words, good job, IMO Jjdon (talk) 19:45, 14 January 2008 (UTC)

• • • 
      

However, this system of calculation gives only the weight of pure gold contained in an alloy. The term 18-carat gold means that the alloy's weight consists of 75% of gold and 25% of alloy(s). The quantity of gold by volume in a less than 24-carat gold alloy differs according to the alloy(s) used. For example, knowing that standard 18-carat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by weight), the volume of pure gold in this alloy will be 60% since gold is much more dense than the alloys used: 19.32 g/cm³ for gold, 10.49 g/cm³ for silver and 8.96 g/cm³ for copper.

This formula gives the amount of gold in cm³ or in ml in an alloy:

$V_{\mathit {Au}}={\frac {M_{a}\times {\tfrac {kt}{24}}}{19.32}}$

where

$V_{\mathit {Au}}$ is the volume of gold in cm³ or in ml,

$M_{a}$ is the total mass of the alloy in grams, and

${\mathit {kt}}$ is the carat purity of the alloy.

To have the percentage of the volume of gold in an alloy, divide the volume of gold in cm³ or in ml by the total volume of the alloy in cm³ or in ml.

For 10-carat gold, the gold volume in the alloy represents about 26% of the total volume for standard yellow gold. One should be aware of this, since talking about purity according to weight could lead to some misunderstandings; for many people, purity means volume.

• • • 
      y is gold counted by karat and not by percent?

International

Can someone double-check the data for Russia/former USSR? The typical value cited in the article is 14 karat, and I'm pretty sure that it was and is higher. —Preceding unsigned comment added by 24.4.205.124 (talk) 23:38, 28 September 2007 (UTC)

initials for gold jewelry

14KP I was told this was plumb gold very pure. I've never heard of this, does any one know?****

Carmen —Preceding unsigned comment added by 70.234.201.86 (talk) 01:39, 16 May 2008 (UTC)

Yes, I know.

Karat Plumb means that it is EXACTLY what is stamped, and no "allowances" or "plus/minus" tolerances are calculated into its fabrication prior to receiving the KP stamp.

So, as to it being "very pure," that is not quite the case. As to it indicating "very accurate," that would be the more correct definition.

14 carat discrepancy

I found another Web site that also described 14-carat gold as 58.5 percent pure; my calculator's telling me it's 58.33 percent. It's not a huge discrepancy, but is one number accepted by industry and one by mathematicians? --Thatnewguy (talk) 16:44, 20 August 2008 (UTC)

It's because you have to solve for karats, not percentage. If you assume you have a gold alloy that has .585 grams of gold (as is claimed) and has a total mass of 1 gram and solve it for X in the equation on the page, you get X=14.04. Obviously, this is rounded to 14 karats for conveinience. --70.184.239.162 (talk) 23:43, 9 September 2009 (UTC)

Karat / carat as a measure of purity?

The text says, "As a measure of purity, one carat is ${\tfrac {1}{24}}$ purity by mass." But the formula shows purity MULTIPLIED by 24, not divided by 24. Is this intentional? --Discostu5 (talk) 22:19, 4 October 2009 (UTC)

Page's definition is wrong

The term "karat" is the correct term when measuring gold purity, while "carat" is actually a term to measure the weight of precious stones. 1 Carat = 200 milligrams. —Preceding unsigned comment added by 41.247.103.64 (talk) 11:01, 16 May 2010 (UTC)

This seems to be a US thing. In the UK, Europe, and most other places, "Carat" is used for gold purity. In fact, I had never heard of the "karat" spelling until I came to this page today. Astronaut (talk) 17:07, 1 April 2011 (UTC)

The second paragraph in "Derivation" contradicts itself.

In the distant past, different countries each had their own carat, roughly equivalent to a carob seed. In the mid-16th century, the Karat was adopted as a measure of gold purity, roughly equivalent to the Roman siliqua (\tfrac{1}{23} of a golden solidus of Constantine I). As a measure of diamond weight, from 1575, the Greek measure was the equivalent of the Roman siliqua, which was \tfrac{1}{24} of a golden solidus of Constantine; but was likely never used to measure the weight for gold.[3]

is it 1/23 or 1/24? — Preceding unsigned comment added by 188.120.133.137 (talk) 10:03, 6 July 2011 (UTC)

therefore

Therefore, 24-Karat gold is fine 99.9 ??

Therefore nothing. Per the formula 24 is 100.00%. Of course you then go on the discuss tolerancing and legalities, but it is nonsense to say 99.9 follows from the definition. — Preceding unsigned comment added by 99.56.162.2 (talk) 14:37, 25 February 2012 (UTC)

International caratages

What is this chart supposed to be saying? Surely all the gold in china isn't 24k. — Preceding unsigned comment added by 99.56.162.2 (talk) 14:44, 25 February 2012 (UTC)

Why 24

I don't feel the article explains why or how 24 became the number indicating the highest purity. It was the weight of a specific coin in carets? How does that turn into a number and term for purity? Some of the comments here mention alchemists which sounds like a reasonable source for the number, because the might have been into numerology and liked the number 24... but where the 24 came from is the only reason I came to this page, and my curiosity has not been satisfied, so I would really appreciate if someone could add some solid information about that. — Preceding unsigned comment added by 76.195.82.81 (talk) 15:24, 5 December 2012 (UTC)

My guess would be that it's because 24 has a lot of factors, i.e. divides nicely by 2, 3, 4, 6, 8 and 12. Similar reason why 12/24/60 appear a lot in time and the old English imperial system. This is my opinion, I haven't got a reference for it. 62.232.221.250 (talk) 09:21, 10 September 2014 (UTC)

Stop removing the section about Volume

It's pointless to remove it. How much space does that section take on wikipedia's servers? 1kB? Don't give me the usual 'not verifiable' argument. It's basic math for Pete's sake! It enlights people who are concern about how much gold their jewelry contains. Suppose I mix 0.75oz of gold with 0.25oz of lithium, it's 18K thus '75% pure' but hey, there's way more lithium in that alloy than gold. I wouldn't call it 75% pure. Calling karat a measure of purity is misleading and one has to wonder if it's not on purpose because a customer buying gold 10K gold jewelry is probably believing it's 42% pure when in fact, there's much more worthless metals than gold. It should be completly illegal. I wouldn't have bought the jewelry I've bought if I'd knew that information sooner. I feel like I've been scammed. In almost every other aspect of life, we measure purity by volume, not by weight. I cannot believe there's scholarly books in the USA that teach both evolution and creationism when the latter has no scientific evidence, but Wikipedia doesn't want to teach how karats relate to volume. Caveat Emptor : Let the buyer beware. That should be one of the purposes of Wikipedia. — Preceding unsigned comment added by 135.19.198.82 (talk) 03:34, 6 February 2013 (UTC)

You still need citations, so people know what you say is true, otherwise they don't know if you

are making up some random stuff or not. Just a citation to a textbook or website won't take too long. It isn't the space that is the problem though. 2001:5C0:1400:A:0:0:0:112D (talk) 17:05, 14 February 2014 (UTC)

Volume is a function of atomic bonds, packing density, etc, and is inherently variable, particularly with temperature. Saying that there is "way more lithium than gold" in an 18K piece of jewellery is simply wrong on any measure which is actually meaningful (either by mass or moles). While this section is useful for those who have not taken an introductory chemistry course, it is misleading in that volume is NOT used to measure purity. Volume is used when there is a known concentration/density as a convenient alternative to mass, as volume is easy to determine, but is not in itself a useful measure and those measurements are converted back to mass or reported when the volume to mass conversion is trivial within common parameters. Volume is not used for purity, and never should be. 150.212.50.15 (talk) 18:55, 11 June 2014 (UTC)

I have tested the claim made about volume with a 34.06g 18k gold bar. Dimensions (in cm) are 1.5 by 1 by 1.45 for a total volume of 2.175 milliliters. Now if 75% of the mass should be fine gold at 19.32g/milliliter, we would have 1.322 milliliter of fine gold (34.06 * 0.75 / 19.32). For 12.5% of silver we should have 0.406 milliliter of fine silver (34.06 * 0.125 / 10.49). And for 12.5% of copper we should have 0.475 milliliter of fine copper (34.06 * 0.125 / 8.96). Now if we add up, we get 1.322 + 0.406 + 0.475 = 2.203 milliliters, about the same volume as initially measured. Now 1.322 / 2.203 = 60% of pure gold by volume, in line with what stated in the wiki article. While it's true that purity isn't measured in volume nor mass but by concentration instead (ppb or ppm), the formula in the wiki article provides a good approximation, which is acceptable for the average Joe non initiated in chemistry. I also encourage you guys to review my results and test it too, for this is how science operates. — Preceding unsigned comment added by 184.160.178.21 (talk) 18:42, 6 October 2014 (UTC)

Karat/carat definition

It says that karat is to measure the purity of Gold, however, I believe it is also used to measure other things, such as diamond and metals other than Gold. Please correct me if I am wrong, but I believe this is correct. 2001:5C0:1400:A:0:0:0:112D (talk) 17:00, 14 February 2014 (UTC)

How 24K gold is sold in jewelry when it's soft?

24K is (almost) pure gold, but pure gold is soft like butter (or so I've been taught). How is it sold in jewelery that's advertised as 24K? I mean, wouldn't this make the jewelry easily perishable? Ai.unit (talk) 15:35, 24 December 2014 (UTC)

It is not that soft. 24K gold is soft compared to other metals but it is not a soft material. If you bite it with your teeth you will leave a small mark but it will hurt your teeth, you will break your teeth before you break a chain.

Plenty of Asian areas use 24K gold for jewellery and it lasts fine for generations. The myth that pure gold needs to be alloyed to be strong enough is spread by western jewellery sales trying to pass off dilute gold to the masses. In many parts of the world 14K gold is considered costume jewellery. Chillum 18:53, 24 December 2014 (UTC)