They made do with low grade ore that still lay on the tip.

This district produced about 50 tons of high grade ore between 1871 and 1895.

No matter the technology, at some point it is too costly to mine lower grade ores.

In addition, until the mills could be built, high grade ore was shipped to California for processing.

And Indian steelmakers so far have not developed the technology to handle the lower grade ore found in the state.

Only the dump of shaft 362 is left today, others have been removed as construction material and low grade ore.

Only the high grade ore was considered useful; the rest of the ore went unused.

Higher international prices allowed medium-sized mines and small producers to mine lower grade ores.

There are also serious technological challenges in exploring deeper, as well producing gold from low grade ores.

Closely spaced fractures of several orientations are usually associated with the highest grade ore.