Wedding anniversary years have well-established connections now common to most nations: 5th Wood, 10th Tin, 15th Crystal, 20th China, 25th Silver, 30th Pearl, 35th Jade, 40th Ruby, 45th Sapphire, 50th Gold, 60th Diamond, and 70th Platinum. In English speaking countries the first, wooden, gift was cut on the day of celebration and then presented to the wife as a finished article before the next two quarter days had passed. The modern tradition may have originated in medieval Germany where, if a married couple lived to celebrate the 25th anniversary of their wedding, the wife was presented by her friends and neighbours with
Gemstone irradiation enabled the creation of gemstone colors that do not exist or are extremely rare in nature. The term "irradiation" is a very broad one, which covers bombardment by subatomic particles as well as the use of the full range of electromagnetic radiation, including (in order of increasing frequency and decreasing wavelength) infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Certain natural gemstone colors, such as blue-to-green colors in diamonds, are the results of the exposure to natural radiation in the earth, which is usually alpha or beta particle. The limited penetrating ability of these particles result in partial