Riddle

tear me apart there is treasure inside,

copper or silver, maybe gold of two kind

the first men may covet the second some have and hide

the first men make, earn, or luckily find

the second belongs to a rare kind of breed

but is the only gold. that when scratched, will bleed

men sails the high seas dreaming of me

but over their hearts, I will always be

the golds that I house, house my identity - what am I?