free mine

例句：

1. 1. The free mine is a treasure trove of rare minerals.
   这个自由矿是稀有矿物的宝库。
2. 2.Mining companies often claim ownership of free mines.
   矿业公司经常声称对自由矿拥有所有权。
3. 3.The government has been trying to unclaim the free mine for years.
   政府多年来一直在试图将自由矿收回国有。