Repairing and recutting a diamond doesn't happen often. It does to diamonds that have been damaged or those that weren't well made when originally cut. it's not too often that a jeweller needs adequate knowledge in the repair or recutting of a diamond. There are some losses due to the lack of a complete understanding of the possibilities.
The most common of all diamond injuries in the trade is the chipping of the edge. Girdle, of the brilliant during the operation of the setting the stone. it's the popular opinion of the public that diamonds are too hard to suffer mechanical injury. However this isn't the case, the use of a careless file can lift tiny flakes from the upper surface of the brilliant. While the diamond is much harder than a file it's not as tough. Most often when a file is misused a thin layer of diamond splits off. The split forms a perfect cleavage of the diamond, which causes it to split easily in certain directions. The rough cleavage will reflect in every part of the stone. This type of serious injury can ruin the stone.
Whenever a stone owned by a jeweller or customer is injured, it should be sent to a competent diamond cutter, who, unless he's instructed to remake it to the ideal proportions, regardless of loss of weight, will use his best judgement in repairing the injury so as to leave the stone in the best saleable condition.
When an injured stone is offered for sale. There isn't an opportunity to have it studied by an expert, the jeweller must look at the stone and decide how much the stone will sell for repaired. When purchasing a damaged stone jewellers will often give low offers. The risk of buying a damaged stone is that, when the repaired stone is sold it won't yield the type of return the jeweller would've expected.
Diamond injuries also occur in the hands of a careless setter. While being worn as jewellery. When diamonds rub together, the sharp edges are worn down. Diamonds are known as angry stones because when they rub together they injure each other, thus loose diamonds should be kept apart. Worn diamonds can of course be repolished. Doing this a number of times will cut down on the weight of the stone.
Another type of injury that happens to diamonds is excessive heating, as in fire exposure. If a diamond is heated to a high enough temperature, it can unite with the oxygen from the air causing blemishes. The damage to the stone can be substantial and fixing it'll result in a loss of weight.
Recutting of diamonds is also worth a lot of attention. Recutting is usually an option when
- Antiquity of the existing make
- Over thickness. Lumpiness exists
- An overspread condition of the diamond
Diamonds in the old-fashioned square or cushion shape, with overthick make and with a large cutlet are known in the trade as old-mine stones. These old mine stones are becoming a bit scarce, most of them have already been cut to modern form. Often old-mine stones end up in the hands of pawnbrokers because most jewellers won't give them the time of day. Often times the old-mine stones are left too thick and are considered lumpy.
Not every old mine stone has the remakings of a fine gem. It pays for jewellers to study cutting and remaking of old gems. Having this type of knowledge will almost always help the jeweller in detecting faulty make in modern cut stones.
In the case of overspread stones the central weakness or fish eye effect can be corrected by recutting to reduce the spread. Spread is a very desirable feature in a diamond, care must be used to not reduce it unnecessarily.