Gemstone industrial abrasives, although larger gem-quality synthetic diamonds are becoming available in multiple carats. Whether a gemstone is a natural stone or lab-created (synthetic), the physical characteristics are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab and do not modify the clarity or color of the stone, unless added intentionally for a specific purpose. Gemstone A gemstone (also called a gem, fine gem, jewel, precious stone, or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other
Volcanic Explosivity Index assignment of a VEI for 7,742 volcanic eruptions that occurred during the Holocene (the last 11,700 years) which account for about 75% of the total known eruptions during the Holocene. Of these 7,742 eruptions, about 49% have a VEI of ≤ 2, and 90% have a VEI ≤ 3. Under the VEI, ash, lava, lava bombs, and ignimbrite are all treated alike. Density and vesicularity (gas bubbling) of the volcanic products in question is not taken into account. In contrast, the DRE (dense-rock equivalent) is sometimes calculated to give the actual amount of magma erupted. Another weakness of the VEI