One material source of diamond is primary diamond mines and ancient placer in the ancient Yi River upstream in Shandong, the other is the primary diamond mine which may exist in this area.
金刚石的物质来源一是古沂河上游山东的金刚石原生矿和古砂矿，二是本区的可能存在的金刚石原生矿。
2
These examples illustrated the economic benefit of the recovery of magnetite, garnet, rutile, gregorite, zircon and building sand that were mined in the placer gold mine.
文中例举的事实表明砂金矿山回收磁铁矿、石榴石、金红石、钛铁矿、锆石及建筑砂石所收到的经济效益。
3
The experience of remining placer gold in Laozuoshan Gold Mine in the past 5 years was introduced. The interior management and technical reform of the gold dredge were summarized.