# How to determine gold content in jewlery.

**URL:** <https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088>\
**Category:** Factual Questions\
**Created:** [April 6, 2005, 8:21pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088 "2005-04-06T20:21:07Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![King\_Friday](https://avatars.discourse-cdn.com/v4/letter/k/43a26b/32.png) [@King\_Friday](https://boards.straightdope.com/u/King_Friday)\
**Post date:** [April 6, 2005, 8:21pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/1 "2005-04-06T20:21:07Z")

</div>

A friend of mine game me some old jewlery to sell on eBay for her. She doesn’t know if they’re 10K, 14K etc. The only thing I can make out on most of them are the numbers 585, and one looks like it says .73. What is all that jazz?

---

<div class="post-metadata">

**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\
**Post date:** [April 6, 2005, 8:49pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/2 "2005-04-06T20:49:12Z")

</div>

It’s a European marking system. It’s basically describing the percentage of gold per thousand. So .73 is basically 73% gold (or 18K) and .585 is about 14K (14/24) by our standards here in the USA.

---

<div class="post-metadata">

**Author:** ![Malodorous](https://avatars.discourse-cdn.com/v4/letter/m/e47774/32.png) [@Malodorous](https://boards.straightdope.com/u/Malodorous)\
**Post date:** [April 6, 2005, 8:49pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/3 "2005-04-06T20:49:49Z")

</div>

I’ve heard that taking a bath is a good way to solve this problem 🙂

---

<div class="post-metadata">

**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\
**Post date:** [April 6, 2005, 9:24pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/4 "2005-04-06T21:24:11Z")

</div>

> [@Malodorous](#):
>
> I’ve heard that taking a bath is a good way to solve this problem 🙂

Eureka!!! 😃

Except… that tactic really only works for disproving that a piece of jewelry is solid gold… or if you know the specific density of the only other ingredient that the gold is alloyed with (which would have to be different than that of gold.)

Otherwise… well, given that a particular object has 85% the density of gold, where do you go from there?? 🙂

---

<div class="post-metadata">

**Author:** ![Malodorous](https://avatars.discourse-cdn.com/v4/letter/m/e47774/32.png) [@Malodorous](https://boards.straightdope.com/u/Malodorous)\
**Post date:** [April 6, 2005, 11:46pm UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/5 "2005-04-06T23:46:32Z")

</div>

> [@chrisk](#):
>
> Otherwise… well, given that a particular object has 85% the density of gold, where do you go from there?? 🙂

I was thinking (to the extent I thought out a throw away joke post) that gold used in jewlery was usually alloyed with silver. A quick google doesn’t confirm that though, so it may be that greeks in bathtubs render us no help in this case.

---

<div class="post-metadata">

**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\
**Post date:** [April 7, 2005, 1:55am UTC](https://boards.straightdope.com/t/how-to-determine-gold-content-in-jewlery/298088/6 "2005-04-07T01:55:29Z")

</div>

Gold that is marked “.750” is 18K. Period. 18K is not marked in any other way.

.585 is 14K.

.417 is 10K(mostly US).

If you truly have something marked “73” then I don’t know what it is.

And the alloy used with gold is copper. Sometimes a very small trace element to make the color different. But the main alloy is copper.