Fluorite crystallizes in the cubic crystal system, forming cubic or octahedral crystals. Fluorite is often found in veins within igneous, sedimentary, and metamorphic rocks. Pyrite crystallizes in the cubic system, and it often forms cubic, octahedral, or dodecahedral crystals, sometimes forming massive aggregates or grains. The bright yellow-golden metallic pyrite provides a bold backdrop for the often vivid green fluorite. The minerals often form together as secondary minerals in areas rich in both iron and fluoride. Specimens that feature large fluorite crystals on well-formed pyrite matrices tend to be more valuable, especially if the fluorite is vibrant in color and the pyrite is in well-defined cubic or octahedral forms.
