What mineralogical knowledge did Li Shizhen record through field investigation in Li Shizhen?

Through on-the-spot investigation, Li Shizhen told a lot of mineralogical knowledge. He said: "There are two kinds of gold: mountain gold and placer gold. Its colors are seven green, eight yellow, nine purple and ten red. Red is full color, silver is soft and the test stone is blue; And copper is hard, and the test stone is sound. " This is a "colorimetric method" still used in modern metallurgy. He described the method of testing the fineness of gold, that is, drawing a line on gold with a touchstone, and comparing the color of the line with the color of the standard sample, the gold content of gold can be estimated. It shows that this method can only be used for gold-silver alloys, but not for gold-copper alloys, and a method to distinguish the two alloys is added. He also described the principle and steps of making aluminum powder, which is the earliest record of making aluminum powder in the world. He also discovered many new mineral drugs, such as Carboniferous. Through on-the-spot investigation and recording folk prescriptions, it played a great role in the completion of Compendium of Materia Medica.