Metal’s prices volatility causes various gold rushes or exploration push creating the need XRF instruments for quickly obtain metal/gold assays. From pawn brokers to jewels and precious metals recyclers. Be sure to be armed with a XRF instruments to not be fooled. XRF instruments are fast, easy to use and precise.  Below is a comparative table for gold assay methods, accuracy and price.

Here a good paper on gold assay methods compared.