Mohs hardness is based on ten common minerals as the standard, which uses mutual scraping to distinguish between soft and hard. Traditionally, Mohs hardness is used to express hardness in mineralogy or gemology. Mohs hardness is divided into ten grades, from soft to hard: talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum and diamond. The understanding of these two concepts will help to understand the concept of ore hardness introduced later.

Raymond mill was originally a manufacturing plant in Berlin, Germany in 1906. Raymond mill was developed on the basis of the first generation of pulverizer. The Raymond Mill centrifugal ring roller mill patent published in the United States at that time was introduced to produce the first Raymond mill.

In the following years, with the continuous improvement of market demand, Raymond Mill's technology continued to improve. According to the processing technology of ultra-fine powder equipment mastered over the years, many manufacturers Raymond mill have carried out comprehensive and thorough technical innovation. During this period, the price of Raymond mill also experienced some changes.