The nearly month-long strike by the United Mine Workers union has cut national coal production in half, mostly by closing mines in the East, and is particularly hurting small, independent coal producers, industry sources said yesterday.

Some of the independents are organizing and seeking a separate peace with the UMW, which since March 27 has been on strike against the Bituminous Coal Operators Association. The BCOA represents 130 caol producers, mostly large and medium-sized mines in the East and Midwest.

About 800 small, independent firms are signatories to the expired 1978 BCOA-UMW contract, but are not members of the association.

"We're suffering tremendously from this strike," said Jack Henry, president of Riverside Industries Inc., a small, independent coal producer in Charleston, W. Va. "We're running the risk of losing out altogether."

Henry's brother, Benjamin, Riverside's executive secretary, said the firm has 150 employes and normally mines 600,000 tons of coal a year. But the strike has brought production to a standstill while monthly expenses approaching $200,000 are draining Riverside's coffers, Benjamin Henry said.

About 40 of the independents, complaining that the BCOA is dragging out the strike at their expense, have formed the Unionized Coal Employers Association in an attempt to work out a separate agreement with the union. Jack Henry, UCEA president, said the group will meet in Charleston tonight to discuss strategy.

UMW officials, however, seem lukewarm to the idea of dealing with a separate group. "I don't think that's going to go," one UMW sourcel said yesterday. Union spokesman Eldon Callen, speaking for UMW President Sam Church Jr., would only say of the development: "We are viewing it with interest."

Industry sources friendly to the BCOA said yesterday they were unconcerned about the move to bargain separately, because BCOA member firms mine about 85 percent of the coal covered by BCOA-UMW agreements. "The independents have tried this before and failed," one source said.

Still, according to a spokesman for the National Coal Association, a Washington-based lobbying group for the coal industry, the strike is having an industrywide effect.

National coal production was down to 8.2 million tons for the week ending April 11, the NCA spokesman said, compareed to 17 million tons a week before the strike.

"It appears that most of the coal being mined now is nonunion coal [in the West]. . . . We're beginning to feel the effects of the strike at this point," the NCA spokesman said.