The differences among colors be immediately obvious or so subtle that direct comparison under controlled conditions is required to discern them. Jadeite and nephrite the jades are much softer and relatively easy to scratch but are perhaps the toughest gem materials. Because of the likelihood of physical damage, hardness tests are NOT recommended for gem identification. Turquoise is often quite porous and can be discolored by exposure to oils. Diamond is the hardest naturally occurring material and is also quite tough however, it can be broken by hard blow.
For example, natural yellow sapphires from Ceylon show distinctive apricotcolored fluorescence, while synthetic yellow sapphires generally show no fluorescence or dull red when exposed to ultraviolet light or Xrays, they transform some of the incoming energy into visible light. Hue is function of the frequency of light and is described by familiar terms such as red, orange, yellow, blue, green, indigo, and violet.
Opals are heatsensitive and have high water content sudden temperature changes or extremely dry conditions can cause them to crack or craze.. The Mohs scale can be misleading there is much greater difference in hardness between corundum and diamond than between and talc. Because of the likelihood of physical damage, hardness tests are NOT recommended for gem identification. Jadeite and nephrite the jades are much softer and relatively easy to scratch but are perhaps the toughest gem materials.
Toughness is resistance to scratching or piercing. Color can be described as the combination of three characteristics hue, tone, and intensity. Jadeite and nephrite the jades are much softer and relatively easy to scratch but are perhaps the toughest gem materials. Tone is variation from very light to very dark. Resistance to chemical degradation or to changes in temperature or humidity are important. This is why two different gemstones have the same size 6. 5 mm in diameter and proportions will weigh approximately carats. Turquoise is often quite porous and can be discolored by exposure to oils.
More precise, and less familiar, measurements of hardness are done using other systems, such as the Knoop scale of resistance to indentation. Hue is function of the frequency of light and is described by familiar terms such as red, orange, yellow, blue, green, indigo, and violet. Intensity is measure of saturation, or purity, of color. Because of the likelihood of physical damage, hardness tests are NOT recommended for gem identification. For example, natural yellow sapphires from Ceylon show distinctive apricotcolored fluorescence, while synthetic yellow sapphires generally show no fluorescence or dull red when exposed to longwave ultraviolet UV light.
Tags: emeralds, natural emerald