หินน้ํามัน หิน ขัด แม่พิมพ์ Fundamentals Explained
When picking a rock for polishing, it’s important to look at its hardness as A necessary variable. Some well known gemstones, for example opal, amethyst, and geode, have various levels of hardness that will affect the time and effort required to polish them.Softer stones like onyx, limestone, or calcite are a sensible choice for newbies since the