A Firebrick triangle Cabochon with calcite inclusions. Size is approximately 18x33mm. A stone that is cut and polished, ready for you to use for your own jewelry creations. It can be used for wire wrapping or even bezel setting, it's all up to you. One of a Kind piece. Copper Firebrick Firebrick is from the old, hand-fired copper smelter of the Calumet & Hecla Mining Co., at Hubbell, Michigan.Hubbell is on the Keweenaw Peninsula, also known as the Copper Country. The old hand-fired smelter was built in 1885/86. But, by the end of the mid-1920's, furnaces were added. The smelter continued to operate until 1968. It was then closed and dismantled from 1968-1973. Over the years, the smelting process resulted in the firebrick asorbing molten copper and other metals from the ore charge. When the smelter was torn down, local rockhounds and lapidaries quickly discovered that the copper impregnated bricks made beautiful clocks, bookends and jewelry. What you have here is a rare piece of Michigan history.