What’s in the Box? Green Eyes

These concentric green circles look like some kind of painting or an old-fashioned LP gone wrong, but in reality this mesmerizing pattern was created by nature. This is the mineral malachite, a copper carbonate associated with ore deposits.

Green malachite "eye"

Malachite forms when other copper minerals like chalcopyrite react with acidic water percolating through the rock. This water can carry copper atoms along for a bit before the copper begins to combine with other atoms and grow minerals like malachite. Sometimes, the water drips into open cavities in the surrounding rock, and malachite will grow as a stalactite or stalagmite the same way other cave formations do.

The photo above shows a slice through a malachite stalactite. The concentric rings come from the growth of the stalactite in fits and starts, and the light and dark colors reflect small changes in the water chemistry over time.

Even though it was made by nature, a little human ingenuity helps this pattern to shine: the rings are most striking in malachite pieces that have been cut and polished like this one.

This post is part of our What’s in the Box? series.

Special Malachite Lapidary Exhibit from Congo on Display

malachite carved face of woman - special exhibit at Rice Northwest Rock and Mineral MuseumWe are excited to feature some malachite lapidary work from the Democratic Republic of Congo (formerly Zaire) in our Lapidary Arts Room for only the month of March 2012. Make time to visit this rare and special collection at the Rice Northwest Rock and Mineral Museum.

malachite carved face - special exhibit at Rice Northwest Rock and Mineral MuseumOn loan from the Ziemer Family, the collection was built between 1975 and 1976 after Mr. Raymond Ziemer was given some pieces as a gift from a local tribe.

Carbonates are a group of minerals that contain the anion group CO32. They can be subdivided into the calcite, aragonite, dolomite or hydrated carbonate groups. The mineral malachite belongs in the hydrated (OH-bearing) carbonate group. It is a copper (Cu) bearing mineral and has the chemical formula Cu2CO3(OH)2. Continue reading