Since your lot is your lot, they have to refine it individually or
they’ll have no idea who gets paid what.
Regarding platinum: I wrote an article called “Refined Manners” for
the October 1999 AJM . If I may, let me quote a quick passage:
"It’s in your best interest to let the refiner know what’s in your
scrap. While all refiners will automatically assay for gold, they will
not go hunting for other metals–platinum is the most popular
request–unless they’re told to. The reason for this is two-fold:
First, it’s costly and time-consuming for the refiner (and that cost
is passed on to the [customer]); second, it avoids potential conflict.
‘Say we just go ahead and assay for platinum, and we only find 0.02
oz., which isn’t payable,’ says [Steve] Warbet [of Republic Metals].
‘We need to get paid for doing the assay, but the [customer] might say
he didn’t ask us to do it.’"
So the upshot is: yes, they can assay for platinum, but it’ll likely
cost you, so be sure the amount in your scrap is worth the expense!