MARCASITE FOR SALE

More About Marcasite

Marcasite is an iron sulfide mineral with the chemical formula FeS₂, the same as pyrite. However, despite having the same chemical composition, marcasite and pyrite differ structurally. Marcasite has an orthorhombic crystal structure, whereas pyrite crystallizes in the isometric system. This structural difference not only affects their appearance but also their stability. Pyrite is more stable, while marcasite is prone to alter over time, especially in humid conditions. Visually, marcasite stands out due to its pale brass color and high metallic luster. Its crystal formations range from sharp spear-like shapes to beautiful radiating clusters, often called “cockscomb” or “petal-like” forms. These formations make it particularly desirable to collectors who appreciate its distinct appearance.

Marcasite typically forms in low-temperature, acidic environments, often in sedimentary rock formations like limestone, shale, and marl. It can also occur as a secondary mineral in hydrothermal veins. Unlike pyrite, which is stable over a wide range of temperatures and pH levels, marcasite requires very specific conditions to form, which makes well-formed specimens rarer and more sought after. Some well-known locales for marcasite specimens include sedimentary deposits in France, England, and the United States, particularly Illinois. It also occurs in various other parts of the world, often in association with minerals like calcite, fluorite, and galena. In some places, marcasite is found as small, decorative nodules or nodular formations that resemble clusters of roses, adding to its appeal as a collectible mineral.

Physical and Chemical Properties

Uses and Cultural Significance

Caring for Marcasite