Have average Diamond Trading Company (DTC) rough diamond prices risen by 16 percent or more so far this year? IDEX Online tries to crack open a small window into the secretive DTC box prices.

In the first four Sights of 2008, the DTC announced a series of price hikes on the rough diamonds it sells, with a cumulative average price increase of 8.5 percent. This week, it was announced that the cumulative hike, including Sight seven, was 16 percent. “Some boxes have been affected more than others,” the DTC noted in the release.

Prices of some sawable boxes rose by more then 10%, the +7, by about 30%

Cross referencing a number of market sources has helped to reveal the price changes on the more than 50 DTC boxes.

Prices on the 5-14.8 carat boxes – such as the fine, crystals and commercial boxes – increased on average by more than 25 percent during the January-June period (Sights 1-6).

Collection boxes seem to have increased by 20 percent. The goods in the collection boxes produce G+/SI+ goods.

Prices of some 2.5-10 carat boxes rose in the lower to mid 20s, but others, like the commons box, increased by only 6-10 percent.

Smaller increases were among the 4-8 grainer boxes. This range used to contain 3-8 grainers, but in April, the +3 grainers were moved into other boxes, creating the 4-8 grainers band. These items, producing 0.20-0.70 carat polished diamonds, rose on average about 7.5 percent between the April and July Sights, with makeables and chips seeing double-digit price hikes in that period – of 10 to 15 percent.

Some boxes, like the colored sawable goods, even saw their prices decrease between the January and March Sights and rise marginally in the following Sights.

Boxes of sawable melees increased in price by a double-digit margin.

One rough diamond trader wondered if some of the price changes in the makeable goods do not reflect a correction in how the price of these goods, which have a high value yield, are calculated.

The DTC, while relatively more open to discuss prices then other miners, is still reluctant to disclose information on its pricing policy. DTC Spokesperson Louise Prior was willing to say that the company had “adjusted prices where we saw that those changes reflected the polished market.”

The boxes mentioned above represent well over half of the boxes the DTC sells – by type, not value or volume.

As the half-year financial results hint – a 10 percent increase in rough sales against a 14 percent decrease in the volume of production – the DTC has clearly raised prices by more than it originally said, hence the Tuesday announcement.

Without knowing the volume of the boxes at each Sight, it is impossible to calculate the average price changes on an entire Sight-by-Sight basis as the DTC does. In the process of researching this article, it became clear that the original 13 percent increase was a low figure.

One thing is clear: even as the DTC price hikes hurt premiums (the increases being noted in the context of mounting premiums), the ‘street’ value of the Sight boxes are still high and demand in the secondary market has yet to be sated. After all, no one is leaving goods on the table.