3.1" Spectacular Sulfur Crystals on Fluorescent Aragonite - Italy

About Sulfur Crystals

Sulfur is a striking and instantly recognizable mineral, prized by collectors for its vivid yellow coloration and its distinctive crystal habits. Chemically, sulfur occurs as S₈—ring-shaped molecules composed of eight sulfur atoms—which give rise to its characteristic resinous luster and translucent glow. In nature, well-formed sulfur crystals typically develop as sharp dipyramids or blocky, tabular shapes. These specimens most often originate in volcanic or sedimentary environments, where sulfur precipitates from sulfur-rich gases or hydrothermal fluids. Many classic localities, such as Sicily or the salt domes of Texas and Louisiana, produce crystals perched on matrixes of gypsum, aragonite, or limestone, creating visually dramatic contrasts.

In the context of mineral specimens, sulfur requires a bit of care. The crystals are relatively soft and brittle, and can fracture if subjected to sudden temperature changes. Because of this thermal sensitivity, sulfur is best stored in a stable environment away from heat sources, bright sunlight, or rapid fluctuations in temperature. With proper handling, however, these luminous yellow crystals remain some of the most eye-catching and iconic mineral specimens in the collecting world.

Aragonite is one of two common calcium carbonate (CaCO3) minerals: the other is calcite, of which aragonite forms as a pseudomorph. Its crystal lattice differs from calcite, resulting in a different crystal shape. It displays a translucent to white color when pure, and when impure can vary between yellow, green, pink, blue and brown. It typically forms in low-temperature hydrothermal veins, in hot springs, and as precipitates from chemicals in sedimentary rock. It can also form under biological processes: aragonite forms naturally in most mollusk shells, and as the calcareous endoskeleton most corals.