Suredaite
Chemical formula: Pb<sup>2+</sup>Sn<sup>4+</sup>S<sup>2-</sup><sub>3</sub>
Suredaite is a rare lead and tin sulfide, forming acicular crystals with a metallic luster.
Description
## Characteristics Suredaite is a rare mineral from the sulfosalt group, chemically classified as a lead and tin sulfide. It forms characteristic, very fine crystals with an acicular or hair-like habit, which usually occur as tangled aggregates, mats, or radial clusters. Its color is black to steel-gray, and the surface exhibits a strong, metallic luster. Due to the small size of the crystals, individual needles are most often visible only under magnification. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness has not yet been precisely determined. The density calculated based on its chemical composition and crystal structure is approximately 6.53 g/cm³, which is a high value, typical for lead-bearing minerals. ## Colors and Varieties Suredaite occurs in a uniform, black or dark gray color. No color varieties or commercial varieties are distinguished. ## History and Name The mineral is named in honor of Dr. Ricardo J. Sureda (born 1942), an Argentine geologist and professor at the National University of Salta, for his contributions to the study of the geology and mineral deposits of the Andes. Suredaite was recognized as a new mineral species by the International Mineralogical Association (IMA) in 2004. Its type locality is the Oploca vein within the Pirquitas deposit in Argentina. ## Uses As a very rare mineral occurring in microscopic quantities, suredaite has no industrial application. It is solely an object of scientific interest and is valued by advanced collectors specializing in rare minerals or sulfosalt systematics.
Diagnostic features
## Identification Characteristic features of suredaite include its black color, metallic luster, and acicular or fibrous crystal form. A key diagnostic clue is its origin from one of a few known localities, in association with other rare tin and lead sulfosalts. ## Distinguishing from Similar Minerals Visual distinction of suredaite from other black, acicular sulfides and sulfosalts (e.g., boulangerite, jamesonite, cylindrite) is practically impossible without advanced studies. Certain identification requires chemical analysis (e.g., EDS/WDS method) to confirm the presence of lead and tin in appropriate proportions, and X-ray diffraction (XRD) analysis to determine the crystal structure. ## Crystal Forms Suredaite forms elongated, acicular or hair-like crystals, which rarely occur individually. Most often, they form dense, tangled aggregates resembling felt or wool, as well as radial aggregates.
Geological environment
## Genesis Suredaite is a hydrothermal mineral. It forms in the final stages of crystallization in polymetallic (silver-tin) veins, under low to moderate temperature conditions. ## Mineral Associations This mineral co-occurs with other sulfides and sulfosalts, such as franckeite, cylindrite, hocartite, miargyrite, aramayoite, as well as with pyrite, galena, sphalerite, and quartz. ## Localities The most important and type locality is the Pirquitas deposit in Jujuy province, Argentina. The occurrence of suredaite has also been confirmed in the San José mine in Oruro, Bolivia. These are the only known localities in the world where it occurs.
Rarity
Very rare
Collector aspects
## Quality Criteria For collectors, specimens where suredaite forms rich, dense aggregates of acicular crystals are of the highest value. Samples where this mineral occurs in association with well-formed crystals of other rare associated minerals, such as hocartite or miargyrite, are also highly prized. Due to the microscopic nature of the crystals, the aesthetics of the entire rock matrix play a key role. ## Popular Localities Collector specimens come exclusively from two locations: the Pirquitas deposit in Argentina and the San José mine in Bolivia. Samples from the type locality (Argentina) are historically more valued.
Care and storage
## Cleaning Suredaite specimens should be cleaned only dry, using a soft brush to remove dust. Due to its acicular form and fragility, mechanical and ultrasonic cleaning should be avoided. Contact with water can initiate oxidation processes. ## What to Avoid Avoid contact with water, acids, and other chemicals that can react with sulfides, leading to their damage and discoloration. The mineral is brittle and susceptible to mechanical damage, so it should be protected from impacts and shocks. ## Storage It is recommended to store specimens in a dry and stable environment, preferably in closed boxes or display cases, to limit access to moisture and airborne contaminants. Protect from direct sunlight.