ขอมูลทั้งหมดนี้ขอขอบคุณ อาจารย์อวยชัย สุภาพจน์ It's not to state that softer stones, like serpentine, cannot be polished, but they have to only be polished with other stones of comparable hardness and never mixed with tougher stones. Wash the rock totally with a scrub brush or old toothbrush to get rid of any https://beediadiamond.com/catalog/polishing-stones