Scratch the quartz surface with a sharp key or a knife. If the quality is high, a grey line will appear, which is the steel powder from the key or knife. You can wipe it off easily. If the quality is low, it will appear a scratching mark on the surface which you can't remove easily. Pure Quartz is clear. Color variance due to impurities: purple (amethyst), white (milky quartz), black (smoky quartz), pink (rose Quartz), and yellow or orange (citrine). Rock crystal quartz is widely distributed, some of the more notable localities being: the Alps; Minas Gerais, Brazil; Madagascar; and Japan. The best quartz crystals from the United States are found at HotSprings, Arkansas, and Little Falls and Ellenville, New York. Quartz and granite maintain their value for many years, and the materials cost approximately the same, with Quartz being slightly less expensive. However, luxurious quartz products can be as expensive as granite slabs. Inhalation over long periods will cause silicosis, where fibrosis of the lungs causes shortness of breath and can lead to death in severe cases. Over-exposure to silica weakens the body's defense mechanisms. Because of the abundance of silica, potential hazards are widespread. Water stains are the most common reason quartz countertop material might lose its luster. When water is left to set into the material, it will cause damage to the finish that seals the countertop. If you are looking for high quality, high purity, and cost-effective Quartz, or if you require the latest price of Quartz, please feel free to email contact mis-asia.