Know Your Rocks

Copper Replacement Agates

A more recent discovery in the Keweenaw Peninsula has been very rare copper-included agates from the Kearsarge Lode. These little beauties are banded agates where some of the banding is replaced by native copper.

The copper sparkle makes them very desirable for distinctive Copper Country jewelry.

These agates require hard labor to recover. I have seen holes on the mine dumps excavated over 8 foot deep where little or nothing is found, but sometimes these agates are found in abundance in one small area. It takes a lot of luck and digging and pounding work to find a good one. You can find these agates with a metal detector but you may also be overwhelmed with false “hits” as you are searching in a copper tailings pile. I just leave the detector alone and dig, later checking the pile I’ve sorted with the detector to see if I missed anything.

These copper/agates are not considered Lake Superior Agates, but are agates from Lake Superior area copper mines. Experts can’t agree on just how these agates formed, but in some way the copper coming up as super heated steam met the silica materials coming down and filled the same vesicles. Seldom are these little agates over a couple inches, which seems to indicate they formed in smaller vesicles in the amygdaloidal basalt. This geology is very interesting, and I know there is some research being done on these unusual agates. You can read more about the formation theories in Agates of Lake Superior: Stunning Varieties and How They are Formed by Bob Lynch.

The agates are commonly light pink and often include blue/green, but I have not seen any as red/orange as is common in the Lake Superior Agates.

The agates have a dark skin and you just do not know what you have until you cut these agates in half. What a great surprise when you find something like the pendant stones I’ve posted in this blog.

I personally know of no other web site that has any copper replacement agate jewelry except this one.  The prices of these agates are based on the rarity and difficulties in finding them. They are much more difficult to find than the elusive Isle Royale Greenstone.