Avoirdupois or Troy !!!

I got the answer of my previous post. Thanks to a friend who pointed me to following ....

1 ounce, avoirdupois = 28.350 grams (approx.) -- this is the ounce used commonly in the US. (There are 16 ounces in an avoirdupois pound.)
1 ounce, troy = 31.103 grams (approx.) -- this is used for precious stones and metals in the US; perhaps it is still used by druggists. (There are 12 ounces in a troy pound.)

Here is the link