U.S. crude's front-month contract closed $7.54, or 10.2 percent, lower at $66.15 per barrel on Friday, its lowest settlement since September 2009.
The front month for benchmark North Sea Brent crude closed $7.54, or 10.2 percent, lower fell about $2 to $70.45, its lowest since July 2010.
While falling prices are not good for oil producers in North Dakota or Texas, it is "unambiguously good" for the American consumer, he added.
That said, he thinks that it will be "quite some period of time" before production of American oil is curtailed.
"It takes so long to bring new product on, to put new pipe in the ground, to put new drills down," Gartman said. "Banks have already lent money on new drilling. You are probably going to have an expansion of crude production here in the United States for at least another six months, maybe nine months."
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After that, he said, there may be a slowing of the increase in production. However, he thinks it will take $50 or $55 crude oil to actually curtail the amount of production in the United States.
"We're going to soon surpass Saudi Arabia, that's something that's going to happen, it's a fact," Gartman said.
—Reuters contributed to this report.