黄金的重量單位

http://en.wikipedia.org/wiki/Ounce#International_troy_ounce
International troy ounce
A troy ounce (abbreviated as t oz) is equal to 480 grains. Consequently, the international troy ounce is equal to exactly 31.1034768 grams. There are 12 troy ounces in the now obsolete troy pound.
Today, the troy ounce is used only to express the mass of precious metals such as gold, platinum or silver.
For historical measurement of gold,

a fine ounce is a troy ounce of 99.5% (".995") pure gold
a standard ounce is a troy ounce of 22 carat gold, 91.66% pure (11 "fine ounces" plus one ounce of alloy material)
http://zh.wikipedia.org/w/index.php?title=%E7%9B%8E%E5%8F%B8&variant=zh-hk

常衡盎司：重量單位。整體縮寫為oz.av。

1盎司=28.350克
1盎司=16打蘭（dram）
16盎司=1磅（pound）

金衡盎司：重量單位。整體縮寫為oz.tr（英）、oz.t（美）。常見於金銀等貴金屬的計量中。

1金衡盎司=31.1035克
12盎司=1 lbs磅
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http://zh.wikipedia.org/w/index.php?title=%E5%85%A9&variant=zh-hk
貴金屬通常係用37.79克為一兩.
由於唔係好知你問既 [兩] 係邊隻, 因為本港既兩[37.79克] 同大陸既兩[50克], 同台灣既兩[37.5克] 都係唔同既, 所以冇換算比你睇, 用 [克]就放之天下都只有一種, 唔會誤會啦.