Johnjamborite
Chemical formula: Pb²⁺₁₄Sb³⁺₈.₅As³⁺₇.₅S²⁻₃₈
Johnjamborite is an extremely rare lead-antimony-arsenic sulfide with a metallic luster, found as microscopic grains.
Properties
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Identification of johnjamborite is possible only through advanced laboratory methods, such as chemical composition analysis (electron microprobe, EDS) and X-ray diffraction (XRD). In reflected light under a microscope, it is white with a creamy tint and exhibits weak pleochroism. ## Distinguishing from Similar Minerals It can be confused with other rare lead sulfosalts, such as madocite or vaughanite, with which it co-occurs. Definitive distinction requires chemical and structural analysis, as all these minerals form microscopic, metallic grains in the same host rock. ## Crystal Forms Johnjamborite forms only very fine, anhedral (irregularly shaped) grains, often intergrown with other sulfosalts. No well-formed crystals have been observed.
Geological environment
## Genesis Johnjamborite forms as a result of low-temperature hydrothermal processes. It occurs in calcite veins cutting marbles formed under conditions of low-grade contact metamorphism. ## Mineral Associations This mineral co-occurs with other rare sulfosalts, such as madocite, vaughanite, jamesonite, as well as with pyrite, sphalerite, boulangerite, and quartz. All these minerals are embedded in a calcite matrix. ## Localities The only confirmed occurrence (type locality) of johnjamborite in the world is Madoc Township in Hastings County, Ontario, Canada.
Rarity
Extremely rare
For collectors
## Quality Criteria As a microscopic mineral, johnjamborite is not evaluated according to typical criteria such as size or crystal form. The collector's value of a specimen lies in the confirmed presence of the mineral, the richness of its association with other rare sulfosalts, and the quality of the analytical documentation confirming its identity. These specimens are of interest only to specialized micromount collectors and scientific institutions.
Care and storage
## Cleaning Due to its extreme rarity and microscopic nature of occurrence, johnjamborite specimens are not subject to cleaning in the traditional sense. Any attempts to clean the host rock should be carried out with utmost caution, preferably under a microscope, using only compressed air to remove dust. ## What to Avoid Contact with any chemicals, ultrasound, and sudden temperature changes should be avoided. The mineral is susceptible to oxidation. ## Storage Specimens containing johnjamborite should be stored in stable conditions, in closed, padded "micromount" boxes, away from dust, moisture, and direct sunlight, to prevent degradation of the mineral and host rock.