Nealite
Chemical formula: Pb<sup>2+</sup><sub>4</sub>Fe<sup>2+</sup>(As<sup>3+</sup>O<sub>3</sub>)<sub>2</sub>Cl<sub>4</sub>·2H<sub>2</sub>O
Nealite is a very rare lead iron arsenate, forming small, prismatic crystals of an intense yellow color.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- Light yellow
- Density
- 5.88
- Cleavage
- Good on {1010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Nealite is recognized primarily by its unique appearance: lemon-yellow, small, acicular or prismatic crystals forming radial aggregates. The location of occurrence – ancient slags in Laurion – is also key. Final identification requires advanced methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Distinguishing from similar minerals Nealite can be confused with other yellow secondary lead minerals, such as mimetite or wulfenite. However, it is distinguished by its crystal habit (small needles in radial aggregates) and specific formation environment. Unlike wulfenite, nealite does not form tabular crystals. ## Crystal forms Nealite crystals are elongated along the [100] axis and have a prismatic or acicular habit. They usually occur as radial or haphazardly tangled aggregates, as well as individual, overgrown crystals on the surface of the host rock.
Geological environment
## Genesis Nealite is a secondary mineral that forms under very specific conditions. It is created by the reaction of seawater with ancient metallurgical slags, remaining after the smelting of arsenic-rich lead and silver ores. It is therefore a product of anthropogenic processes occurring in an environment similar to natural ones. ## Mineral associations This mineral co-occurs with other rare secondary minerals formed in the Laurion slags, such as laurionite, paralaurionite, fiedlerite, penfieldite, anglesite, cerussite, and goethite. ## Locations The only confirmed occurrence of nealite in the world is the ancient slag heaps in the Laurion district, Attica region, Greece. This is its type locality.
Rarity
Very rare
For collectors
## Quality criteria The most prized nealite specimens are those with well-formed, sharply terminated crystals of an intense, lemon-yellow color. It is important that the crystals form aesthetic, radial aggregates on a contrasting matrix (host rock or another mineral). Due to the microscopic size of the crystals, their sharpness and lack of damage, visible under magnification, are crucial. ## Popular localities The only source of nealite specimens is its type locality – Laurion, Greece. All specimens available on the collector's market come from this single location.
Care and storage
## Cleaning Nealite specimens are extremely delicate and usually very small. Mechanical cleaning is not recommended. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and any chemicals. ## What to avoid Avoid ultrasonics, steam cleaners, acids, and solvents. The mineral is sensitive to shocks and abrasions. As a secondary mineral, it may be unstable in conditions of high humidity or temperature changes. ## Storage It is recommended to store specimens exclusively in specialized micromount boxes, which protect them from mechanical damage, dust, and humidity changes. Avoid exposure to direct sunlight.