Galena is often found in metamorphosed rock, like this mountain range.
The mineral galena, also known as lead sulfide, fits into the sulfide classification. The two elements, lead and sulfur, chemically combine to form galena. It's commonly associated with other metal sulfides, such as sphalerite (zinc sulfide) and marcasite (iron sulfide) in altered rocks. It can be found in several different rock environments.
Metamorphic Rocks
Rocks become metamorphosed when they are changed by physical conditions, like the addition of heat and pressure. If chemically active fluids, such as magma, are present, they contribute elements to the environment that were not there originally. The most common formation of galena occurs in metamorphosed rocks, where it's found with pyrite (iron sulfide) and chalcopyrite (copper iron sulfide).
Hydrothermal Alteration
Hydrothermal alteration happens when sedimentary and volcanic rocks are altered by the introduction of water and heat. The heat usually comes from magma chambers underground. The water source is groundwater. The water travels through fracture systems, leaving behind minerals that combine into new rock formations. Galena develops in the fractures with quartz, bornite (copper iron sulfate) and sphalerite.
Vein Deposits
Galena forms as crystals in shallow ore veins. It's present with silver, the other sulfides and other minerals such as quartz, dolomite (calcium magnesium carbonate), fluorite (calcium fluoride), calcite (calcium carbonate) and barite (barium sulfate).
Disseminates
Minerals said to be disseminated throughout a rock appear in small crystals spread throughout a rock. Galena can be found disseminated throughout hydrothermal deposits.
Igneous and Sedimentary Rocks
Igneous rocks form from melts (magma) while sedimentary rocks result from the deposit of sediment in lakes and stream beds. Galena found in these types of rocks is associated with the same minerals as it is in the other environments.
Tags: iron sulfide, associated with, copper iron, disseminated throughout, Galena found, throughout rock