At the last speaker evening meeting of the current season, members of the Probus Club of Basingstoke had the pleasure of one of their members giving a talk on his experiences as a diamond polisher. Chris Barton, ably assisted on the evening by his wife Jenny, who live in Robin Close, Kempshott, had worked for the Basingstoke company, L M Van Moppes who were then based in Lister Road.
Less than 20% of diamonds are suitable as a girl’s best friend, the majority being used for industrial applications. Originally an engineer for the company making diamond cutting tools, Chris moved into the highly skilled area of diamond polishing. And it was this side of his involvement with this trade that he was able to educate his audience of retired professional and business men at their meeting at Christ Church in Chineham.
To create a diamond normally requires three conditions, those of temperature, pressure and time. The basic material has to have a carbon content which is exposed to 900 – 1300 degrees Centigrade, under pressure of approximately 400 tons per square inch, over 1 – 3.3 billion years. This time period is up to 75% of the age of the Earth. It had also to be in a stable environment below continental plates at a depth of 90 – 120 miles. Eventually as a result of volcanic activity magna was forced to the surface becoming igneous rock containing its precious cargo.
But there is another scenario that has the conditions for the creation of a diamond which is a meteor strike. There is evidence of this in the Russian Popigai crater in Siberia which is the seventh largest verified impact on Earth, occurring approximately 35 million years ago. The impactor was calculated to have been 5 miles in diameter and made a crater 62 miles wide. The shock pressures from the impact instantaneously transformed graphite in the ground into diamonds within a radius of over 8 miles of the impact point. However the diamonds from this area are only suitable for industrial applications and are not fit for the jewellery market.
Pure diamonds are transparent but some are coloured by nitrogen which gives a yellow or brown tinge, or a blue tint caused by baron. Gems are priced according to the 4Cs; carat, cut, colour and clarity. A single cut diamond will have 18 facets while the larger gem stone has 58 facets equally cut above and below its girdle. The final weight of a cut and polished stone is half of its original weight but the residue is saved for industrial use.
Potential members of the Probus Club of Basingstoke, which has been in existence for nearly 35 years, can visit their web site http://www.probusbasingstoke.wordpress.com to see their various activities or call their secretary Bryan Harvey for an informal chat on 01256 321473.