What are the Tertiary auriferous gravels?

Tertiarius is a genus of freshwater diatom known from the fossil record

You dig it up from the earth.

Tertiary means the third in order ,hierarchy or level in sequence in structure , event or activity.

Gravel has a specific meaning in both Civil Engineering and Geology. In both cases it is related to the diameter of the grains which the soil is composed of. Gravels are composed of grains of sizes...

Don't know if it'll work for gravel, but in hauling asphalt, we have a couple different means. At every asphalt plant, there'll be a dispenser, which dispenses a soap and water mix to keep the beds...