DANVILLE — A 300-million-year-old “fossil forest” discovered in a coal shaft 30 miles south of Danville will again become invisible to human eyes as miners seal areas where they have already extracted the coal and moved on.

“Most of that stuff is already sealed up,” said Eric Quan, Vermilion Grove mine manager.

“Us old coal miners have seen these things for years and didn’t think anything about it,” he added. “That’s what coal is made of.”

But the geological community became excited when it was determined the fossilized tree stumps and fern leaves the coal seam had exposed was part of a 4-mile swath of an ancient rain forest.

“The fossil ceiling, held up by 6-foot-high, 80-foot-wide pillars of coal, goes on for 4 square miles,” said a 2008 article in Discovery Magazine. “No other known preserved forest comes close in size.”

The forest is found in the Herrin coal seam which runs through both the Vermilion Grove mine and the Riola mine in Indiana.

Peabody spokeswoman Beth Sutton said the mine had gotten increased scientific media attention after the Illinois State Geological Survey went down into the mine for survey and fossil collection.

She said the requests for tours and interviews became overwhelming to the point where the company could only grant a few because of the manpower needed to ensure an outsider’s safety in the mine.

Quan said he started referring calls to corporate spokespeople after a story on the discovery ran in the Los Angeles Times.

“That’s when it really started to pick up steam,” he said, adding he believes the initial media rush was partially because that article had incorrectly converted hectares into miles, showing the forest to be four times larger than it really was.

Still, scientists had a field day with the rare view from underneath a forest that had been destroyed with a mud flow that, 300 million years ago, took four months to play out. The slow mud preserved the forest as opposed to a catastrophic event that might have destroyed fossil evidence. It’s the same process that created the numerous coal deposits that brought early settlers here.

“It’s the worm’s-eye view. You’re looking up at what the forest floor used to look like,” said Scott Elrick, the ISGS geologist who surveyed the find, in the Discover article. Elrick could not be reached in time for this story.

He said in his ISGS report that the opportunity to research the forest was one he savored: “When fossil plant researchers (paleobotanists) want to look at the ecology of an ancient forest, it is rather difficult to simply go walking through an ancient forest.”

Elrick surmised an earthquake dropped one side of the fault and caused flooding.

“Because the subsequent influx of sediment was not a catastrophic tsunami thing but more of a slow-motion event, all the small itty-bitty plants are in place,” he said in the Discover article.

Quan said workers were glad the attention is behind them.

“It was really more of an inconvenience,” he said.