Caterpillar's mining business is down in a hole.

Its third-quarter earnings plunged 44 percent and it cut its forecast, again. It said revenue will be almost $11 billion lower than last year, a drop of 17 percent. Most of the decline is in its mining gear business, where revenue is expected to fall 40 percent.

"With $11 billion coming off the top line, it has been a painful year and has required wide ranging and substantial actions across the company," Chairman and CEO Doug Oberhelman said in a statement.

Until this year, rising commodity prices had fueled a mining boom. But slower growth in China's economy hurt demand for mining gear there as well as in Australia. Revenue in its "Resource Industries" unit, which is mostly mining, plunged 63 percent in the Asia Pacific region.

Caterpillar has already been shutting factories and cut its workforce by some 13,000 people, and temporarily laid off thousands of salaried workers. It said it has also cut its capital spending plans for the year. At the end of the quarter it employed 121,506 people full-time worldwide.

The Peoria, Ill., company earned $946 million, or $1.45 per share, in the quarter that ended Sept. 30. That was down from $1.7 billion, or $2.54 per share, in last year's quarter.

Revenue tumbled 18 percent to $13.42 billion.

Analysts had predicted earnings of $1.68 per share on $14.29 billion in revenue.

Even with the slowdown, it still posted operating profits in each of its units. Besides mining gear, Caterpillar makes construction and forestry equipment and large power generators.

Sales in its Resource Industries unit, which includes mining, fell 42 percent to $3 billion. Construction revenue fell 7 percent to $4.55 billion as dealers reduced inventory. Generator sales fell 7 percent to $4.92 billion.

Caterpillar Inc. now expects 2013 earnings of about $5.50 per share, down $1 from its previous forecast. It also dropped revenue expectation to about $55 billion from $56 billion to $58 billion. The company also lowered its earnings and revenue expectations in July.

Caterpillar shares fell $5.14, or 5.7 percent, to $84.03 in morning trading.