Perlite can keep the pile healthy. Volcanic rocks are very suitable for pile support, and volcanic rocks containing perlite 1 are more suitable for pile support than 1. Zhu Yan is an acidic lava ejected from volcano, which is glassy rock after rapid cooling, so it is named because of its pearl-like fracture structure. Perlite minerals include perlite, obsidian and turpentine. The difference between the three is that perlite has a circular crack formed by condensation, which is called perlite structure, and its water content is 2~6%. The turpentine rock has a unique turpentine luster, with a water content of 6~ 10%. Obsidian has glass luster and conchoidal fracture, and its water content is generally less than 2%.