These attractive lime green fluorites occur covered in Quartz, in this remote south African mine. As part of the prepping, the fluorites are immersed in Hydrofluoric acid (think of the blood in the movie Alien that dissolves metal) that dissolves Quartz but not the Fluorite. There are current major problems with production at the mine, and future mining is uncertain. 

This piece is a beautiful contrast of green Fluorite and well crystallized Quartz crystals growing right off the front face of the flourite! There is a smaller fluorite that is covered in druzy Quartz crystals that also serves as a contrast to show how these amazing minerals form.