pearl necklace (oo er)

[911newbie]

Ladies and Gents
Any ideas where I can read some info on buying pearls ?
I'm thinking of buying my OH a pearl necklace (as in a string of pearls) and don't know what to make of the various options, freshwater vs Akoya etc etc.

So for example is this a bargain -
http://www.pearlsonly.co.uk/japanese-akoya-pearls/...

Thanks for any help you can provide.

MODS: I figured this was about the most appropriate forum for this.