Improvements in or relating to a method of testing a sample of quartzite for use as source material in a hydrothermal quartz crystal growing process

摘要

A sample of quartzite for use as source material in a hydrothermal quartz crystal growing process, is tested by irradiation with X-rays and observing whether or not there is darkening of the quartz crystal grains in the quartzite. When darkening is observed this indicates that the aluminium present in the quartzite will form simple ions in a solution of the quartzite in sodium carbonate solution, which aluminium will tend to replace silicon atoms in a quartz crystal grown from the solution; to grow good quality quartz crystals from such quartzite, a process described in Specification 797,203 is used, employing a solution of sodium carbonate, sodium hydroxide and sodium fluoride. When no darkening is observed this indicates that the aluminium will not be available in solution to replace silicon atoms in a crystal grown using this quartzite, and a process described in Specification 811,214 may be used employing a sodium carbonate solution. A thin slice is cut from a piece of the quartzite and mounted on a backing plate, such as of glass, and irradiated with a dosage of X-rays between limits such that it is not sufficient to darken a synthetic quartz crystal but will darken melting quality rock crystal; a dosage of 5 X 106 Rontgens is suitable. Part of the sample may be shielded by a lead screen to allow comparison to be made. Specification 811,215 also is referred to.