Goldtown Adventures is an awesome series by Susan Marlow, author of the Andrea Carter Circle C Adventure Series.
This is the 2nd in the series.
From the Author:
Goldtown’s in trouble. When Jem is caught in a miners’ riot, he learns the worst: the Midas mine has run out of gold. A new vein deep underground shows promise, but an old mine nearby must be reclaimed for an air shaft. However, Jem’s friend Wu Shen and the other Chinese are working those abandoned diggings, and they refuse to give up their lawful claim–not even to save the town. Soon, Jem’s sheriff father is ordered to evict the Chinese or lose his job. Then Will, the mine owner’s son, comes up with a plan. If Jem goes along with it, Pa can keep his job, and the Midas will get its air shaft. Sounds like a great idea . . . until Will’s risky plan leads to disaster deep inside an old mine.