The market assortment underlying RoughPrices.com is based on that used by WWW International Diamond Consultants Ltd (www.diamondwww.com).
There is no standard price list for rough diamonds and there is no certification system for individual stones unlike for polished diamonds.
A rough price list can vary from over 15,000 price points as with De Beers to much simpler ‘market’ price lists such as being used by RoughPrices.com.
In pricing rough it is the combination of an assortment of diamond categories based on their colour, type/shape/form and quality/clarity as related to the rough price list being used which is the key to determining the value of a diamond(s).
In the RoughPrices list the colour of diamonds (a key determinant of value) is not shown separately but is sorted in with the quality.
A more detailed description of what is included in each price point is listed below.
It must always be remembered that valuing rough diamonds has a high degree of subjectivity. Values for individual stones can vary dramatically between experts. However with a large parcel of diamonds these differences average out and agreement overall over the value of an individual parcel is usually within a few percent of current market prices.
Theoretically the value of rough is based on the value of the polished whicht that particular rough will produce. Whilst there is some correlation between rough and polished they are in fact both very separate markets working under different dynamics where at any one time the differences between the two can be substantial.
One problem with valuing rough diamonds is that there can be legitimately differing views as to what the likely outcome in polished terms there maybe from a particular stone or even a parcel of rough, though as the number of stones increases this tends to become considerably less of a factor in determining value.
The initial supply of rough into the market is relatively highly controlled with De Beers having about 40% of the market. Taking the five major producers of rough, De Beers, Alrosa, Rio Tinto, Dominin Diamond Corp they represent well over 75% of world production. Polished in contrast is an extremely fragmented market.
Rough is supply driven and prices especially in relation to polished diamond prices have to be viewed in this context.
RoughPrices.com prices format is based on that used by WWW International Diamond Consultants Limited.
In addition to WWW providing prices each month a small number of companies are canvassed on their prices and the prices used are the average of those views.
Any valuation of rough depends as much on the assortment as on the actual price list. A general description is given as to what is included for each price point. However it must be stressed that these are general guidelines. Each price point is designed to cover a range of diamonds of different values. When sorting a parcel for valuation there are no absolutes and common sense has to be used. For example if a parcel has a particularly high average colour it might be decided to add a certain percentage to the overall price. It is not possible to create absolute rules for valuation. Indeed the more complex a price list, designed to compensate for this very issue, there are many that argue that the very complexity reduces accuracy as the increased number of price points also increases the problem of overlaps between one category to another.
The RoughPrices.com format has proven to work and gives a sound basic guide to the current market price for rough.