Before the technological means were found in the mid 19th century to fashion the outline of a diamond to shape a perfect circle, the circumference of polished brilliants followed the outline form of the rough diamond from which the brilliant was fashioned.

Old brilliant cut diamonds are characterised, when compared to the round brilliants we see today, by their small table facet size, large culet facet and thick crown dimensions. The retention of maximum weight from the rough was an important consideration when cutting, so old cut brilliants have greater depth in respect to their width, than today's round brilliants. Therefore the brilliance of older brilliants may not be as high and the amount of light returned to the eye ('life') from the smaller table facets of the older stones is less than that created by modern round brilliants. This explains why older stones are not as optically brilliant as modern stones.

However, the larger crown facets and thick crown heights possessed by the older brilliants means they exhibit a greater degree of dispersion ('fire') than their modern counterparts. This optical attribute is best exposed in lighting that has small point sources such as candle-light or modern spot lighting; old cut stones do not appear their best under modern fluorescent strip lighting. Old cut brilliant diamonds were fashioned at a time when candle light and gas light were the principal means of illuminating rooms so old cut stones look much better than modern stones in low levels of candle light illumination when the full beauty is displayed. Those who handle antique diamond jewellery will have experience in scrutinising old cut diamonds. Up to quite recently, many old cut diamonds were lost to us because of the tendency for many in the gem and Jewellery industry to re-cut old cut stones into the modern round brilliant style.

Old cut stones were not considered as desirable or as valuable as the more modern round style. Any old cut stone of commercial quality that would yield a modern brilliant of appreciable size, e.g. half to one carat or more would be refashioned. In the past gem laboratories would see many old cut stones submitted for grading by dealers seeking to know whether the diamond could be re- cut to a certain acceptable size and quality. Sadly many attractive shaped old diamonds were altered and lost to us forever. That trend to re- cut now seems to have stopped. It has occurred to dealers and retailers that the consumer may be looking for something different - an old cut stone, an item that is not as common to see as a modern cut diamond.

To describe the symmetry grade of this older style of diamond adequately is something of a challenge. It seems unjust to judge the symmetry elements, such as an off-centre table facet, variation in crown height, an off-centre culet and a non-symmetrical outline of the girdle, against grading standards devised to assess modern diamonds fashioned with technology and knowledge only available to today's diamond cutters. Old cut Diamonds tend to "mask" their true body colour especially when mounted in a piece of jewellery for the following reasons: They were hand faceted with less than concise proportions and consequently do not reflect light as brilliantly as does their modern faceted counterpart: "The Modern Round Brilliant."