Hugotibergite
Chemical formula: Ca<sub>6</sub>CaPb<sup>2+</sup><sub>2</sub>(Si<sub>3</sub>O<sub>9</sub>)<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>
An extremely rare calcium and lead silicate-sulfate mineral, known exclusively from the famous Långban deposit in Sweden.
Properties
- Crystal system
- Monoclinic
Diagnostic features
## Identification Macroscopic identification of hugotibergite in the field or in a collection is practically impossible. Definite identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical analysis using an electron microprobe (EPMA) or scanning electron microscopy with an EDS detector. ## Distinguishing from similar minerals It occurs in association with many other rare lead and calcium silicates typical of the Långban deposit (such as margarosanite or roeblingite). Distinguishing it from these minerals based on external features is impossible and always requires laboratory verification. ## Crystal habits It crystallizes in the monoclinic system. It usually forms microscopic crystals or fine, irregular aggregates within the host rock, rarely showing well-formed crystal faces visible to the naked eye.
Geological environment
## Origin It forms under specific geochemical conditions of metamorphosed iron and manganese skarn-type deposits. This environment is characterized by an extraordinary abundance of trace elements, including lead, barium, arsenic, and antimony, which form unique mineral phases under contact metamorphic conditions. ## Mineral associations It co-occurs with other rare minerals typical of the Långban deposit. It is usually accompanied by complex calcium, lead, and manganese silicates, as well as oxides and carbonates characteristic of skarn zones in this region. ## Localities The only confirmed locality (type locality) is the Långban mine in the Filipstad ore district (Värmland region, Sweden).
Rarity
Extremely rare
For collectors
## Quality criteria In the case of such rare minerals, the value of a specimen is primarily determined by the simple confirmation of the species' presence on the sample, preferably supported by a certificate or laboratory analysis results. An additional asset is the size and clarity of the crystals under a stereomicroscope. ## Popular localities The Långban mine in Sweden is the only source of this mineral. This locality is one of the most famous places on the world mineralogical map, highly valued by collectors of rare species due to its enormous number of type minerals.
Care and storage
## Cleaning Specimens containing hugotibergite should be cleaned exclusively using compressed air or gentle rinsing with distilled water. Mechanical brushing and ultrasonic cleaners must be strictly avoided, as they could destroy the microscopic crystals or cause them to crumble from the rock. ## What to avoid Due to the presence of hydroxyl groups and water molecules in the crystal structure, heating the specimens should be avoided. The mineral should be protected from acids and strong chemicals that can react with lead and calcium, leading to irreversible surface damage. ## Storage Specimens should be stored in a dry, stable environment. Closed micromount boxes or transparent acrylic containers are the best solution, protecting delicate samples from dust, moisture, and accidental mechanical damage during handling.