Northstarite
Chemical formula: Pb<sup>2+</sup><sub>6</sub>(Te<sup>4+</sup>O<sub>3</sub>)<sub>5</sub>(S<sup>6+</sup>O<sub>3</sub>S<sup>2-</sup>)
Northstarite is an extremely rare lead thiosulfate and tellurite, forming microscopic, canary-yellow crystals with an adamantine luster.
Properties
- Luster
- Adamantine
- Streak
- Light yellow
- Density
- 6.51
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Key features for preliminary identification of northstarite are its canary-yellow color, very strong adamantine luster, high density, and specific environment of occurrence. However, definitive identification is impossible without advanced laboratory analyses, such as X-ray microanalysis (EDS/XRD), due to the microscopic size of the crystals and similarity to other secondary tellurium minerals. ## Distinguishing from Similar Minerals Northstarite can be confused with other rare, yellow minerals from the oxidation zones of tellurium-rich deposits, such as emmonsite, mackayite, or paratellurite. Distinguishing it with the naked eye or under a loupe is practically impossible. It requires analysis of chemical composition and crystal structure. ## Crystal Forms This mineral most often forms aggregates or crusts composed of very small (usually less than 1 mm), platy or bladed crystals. Crystals in aggregates often show sub-parallel arrangement.
Geological environment
## Genesis Northstarite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of polymetallic, hydrothermal ore deposits rich in tellurium. It forms as a result of the weathering of primary tellurides and lead sulfides under low temperature and pressure conditions. ## Mineral Associations It most often co-occurs with other secondary tellurium minerals, such as schieffelinite, paratellurite, tellurite, as well as with primary minerals like galena, pyrite, and quartz, which constitutes the host rock. ## Localities The most important and classic occurrence is the type locality – the North Star Mine in the Tintic District, Juab County, Utah, USA. Its presence has also been confirmed in the Bambolla Mine in Moctezuma, Sonora, Mexico. These are the only known, well-documented occurrences of this mineral in the world.
Rarity
Extremely rare
For collectors
## Quality Criteria In the case of such a rare micromineral as northstarite, the collector's value is primarily determined by the richness of the specimen – i.e., the quantity and density of crystals on the rock matrix. The quality of the crystals themselves (sharpness of edges, luster) and the presence of associated minerals, especially other rare tellurates and tellurites, are also important. The more intense the color, the more desirable the specimen. ## Popular Localities The most prized and sought-after specimens by collectors come from the type locality at the North Star Mine in Utah. Material from the Mexican Bambolla Mine is also valuable, but American finds are considered classic for this species.
Care and storage
## Cleaning Northstarite specimens are extremely delicate and small. For dust removal, it is best to use compressed air from a safe distance. Any contact with water or chemicals is risky. If absolutely necessary, very careful, brief rinsing in distilled water and immediate drying is permissible. ## What to Avoid As a lead mineral, northstarite is toxic – avoid inhaling dust and wash hands after any contact. Absolutely avoid all chemicals, acids, detergents, and ultrasonic cleaners. It should be protected from high temperatures and prolonged exposure to intense light. ## Storage The safest storage method is to place the specimen in a sealed "micromount" box with an appropriate label. It should be kept in stable conditions, away from moisture, light, and heat sources, to prevent its degradation.