One of the most consistent correlations in investing — the dollar goes up, commodities go down — is no longer a given, and that has commodities trader Dennis Gartman concerned.

"What we're seeing is a lesser respect for the U.S. dollar, and a greater use of other currencies to buy commodities," the widely followed editor of the Gartman Letter told CNBC's "Fast Money" traders on Monday.

The correlation, Gartman points out, comes from the fact that most commodities are priced in dollars. When the dollar strengthens, commodities are driven down because more of that commodity can be purchased for the same dollar. Conversely, when the dollar weakens, less of that same commodity can be purchased with the same dollar, driving up the value of the commodity.

But Gartman says this correlation is on its way to becoming extinct.

According to Gartman, countries are changing their pricing mechanism to cut out the need for the U.S. dollar. Instead, Gartman contends, investors are buying commodities in the currency of their choice and cutting out the middle man.

"We might be seeing more pricing of crude oil in Asia in renminbi terms. We may be seeing greater pricing of grains in Europe in euro terms. We may be seeing a greater pricing of base metals in yen terms in Asia," said Gartman. "I think that's really what's happening here."

Currencies such as the euro and the yen have soared 5 and 9 percent, respectively, against the greenback since the beginning of the year.

"This all began because of a loss of confidence in the U.S. to begin with," said Gartman. "We are less strong than we used to be, and we're perceived to be weakening."