Platinum ore identification

Can anyone tell me where I can send a small piece of ore for assay to
tell the content of the material. It is believed to possibly be
platinum. The small piece brought to me by my client was very
laboriously chiseled away from a larger but compact piece weighing
almost 7 lbs. This was found hidden in the behind the drywall of a
wall in a very old house being remodeled. Any direction would be
appreciated. I can email a pic if that would help.

Thanks.