Assays are slow not due to the assay method employed but due to the sample preparation which takes long time. A few days are enough to report the assay results if the samples are ready.

Normally the full drill cores taken from the underground have to be cut into half cores (or even quarter cores), and store 1/2 of the half cores for future use.

Imagine the time needed to cut 500 m of full drill core into half drill core by a saw.

The remaining half core samples are cut meter by meter. there would be 500 samples if the hole is 500 m in depth.

Each meter sample has to be crushed (say to 10 mesh) and then further pulverized to very fine before sending out for chemical assaying.

you need to log in the cores properly before doing all of above.

Hope this will help.