According to the recently launched Zimnisky Global Rough Diamond Price Index, prices for the precious rocks have fallen 9.4% in the past year, squeezing producers profits.

Diamond mining is particularly complex since a miner’s revenues and profits depend not only on how many stones it mines — measured in carats — but also on the prices it gets for the output. And this can vary quite a bit from mine to mine and from rock to rock.

That complexity motivated diamond expert Paul Zimnisky, in part, to launch a new index aimed at consolidating reliable rough diamond price information and update changes on a weekly basis.

“Given the highly concentrated state of the diamond mining industry and the relatively opaque nature of rough diamond trading, indicative rough diamond price information has historically been hard to come by,” Zimnisky said in a press release.

He noted his index intends to track, analyze, and disseminate aggregate rough diamond price changes on a more frequent, more easily accessible basis than what is currently readily available to investors of diamond mining equities, analysts, and diamond industry participants.

The Index is based on an initial value of 100 using data starting on April 4, 2004, and is currently valued at 163.41 as of July 3, 2015.