Learning gold ..the hard way

[Jake]

Hello everybody , ive a question i cant figure out.It would seem straightforward ..however , its to do with weight,purity and size.Two coins in question , one is a 1910 US quarter eagle , beautiful wee coin weighing in at 4.18g.Its almost if not exactly the same size as a dime..900 gold which as i understand is 22k.

The other coin in question is a 1911 George V half sovereign.Its a millimeter and a half bigger in diameter,minimally thicker..so bigger all round.

It too is .900 22k.. so why does it weigh less than the quarter eagle ?

This isnt just my two coins,the recorded weights match with everything ive read,the half sov is lighter but bigger..why ?

[Gary D]

Just a suggestion, perhaps you need to compare the flan size not the finished coin size. The half sovereign may by slightly bigger but have less metal in the design, deeper rims etc.

[VickySilver]

Half sov is 4.00 gm of 22k (which is 0.916). If math is right that is 3.664 net gm. versus the 4.16 x 0.900, or 3.74 gm. pure gold....

[Chris Perkins]

The US coin is .900 gold which is a wierd sort of decimal fineness of exactly 90% (as used in Germany and other European countries). It's somewhere between 21 and 22 carat. British gold is spot on 22 carat which is actually .916 fine (91.66666666667%).