Lanarkite
Chemical formula: Pb<sup>2+</sup><sub>2</sub>O(S<sup>6+</sup>O<sub>4</sub>)
Lanarkite is a rare, secondary lead sulfate, forming white or greenish, acicular crystals, often with a pearly or resinous luster.
Properties
- Mohs hardness
- 2-2.5
- Luster
- Pearlescent, Resinous, Adamantine
- Streak
- White
- Density
- 6.8-6.9
- Cleavage
- Perfect on {001}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of lanarkite include its crystal forms (elongated, platy crystals), high density (the specimen is heavy for its size), softness, and pearly luster on cleavage planes. It often occurs in association with other secondary lead minerals, such as cerussite or anglesite. ## Distinguishing from Similar Minerals Lanarkite can be confused with cerussite and anglesite. Cerussite is harder (3-3.5) and often forms reticulated aggregates. Anglesite is also harder (2.5-3) and has different crystal forms. Final distinction often requires chemical or crystallographic analysis. ## Crystal Forms Lanarkite crystals are monoclinic but often exhibit pseudo-orthorhombic symmetry. They are usually elongated along one axis, forming platy, acicular, or hair-like forms. Crystals can be slightly bent and often form fan-shaped or radial aggregates.
Geological environment
## Genesis Lanarkite is a secondary mineral, forming in the oxidation zones (so-called iron caps) of lead ore deposits. It forms as a result of the weathering of galena (PbS) and other lead sulfides under conditions of low carbon dioxide content. It can also form as a product of the reaction of acidic mine waters with lead minerals. ## Mineral Associations This mineral often co-occurs with other secondary minerals of the oxidation zone. The most common associated minerals are cerussite, anglesite, leadhillite, susannite, as well as calcite, galena, and sphalerite. ## Localities The most important historical locality, from which classic specimens originate, is Leadhills in Scotland (United Kingdom). Other known localities include the Susanna mine in Lavrio (Greece), mines in the Sierra Gorda region in Chile, the Kintore mine in Broken Hill (Australia), as well as some deposits in Arizona and Idaho (USA).
Rarity
Rare
For collectors
## Quality Criteria The most valued by collectors are specimens with well-formed, sharp, and undamaged crystals, especially those forming aesthetic, radial aggregates. Transparent crystals with a distinct luster are desirable. A contrasting association with host rock minerals or other associated minerals (e.g., with leadhillite) significantly increases the specimen's value. Crystal size is crucial – specimens with crystals exceeding a centimeter in length are rare and highly prized. ## Popular Localities Classic, most valued specimens come from the type locality in Leadhills, Scotland. Very good quality crystals were also found in the mines of Lavrio, Greece, and the Kintore mine in Broken Hill, Australia.
Care and storage
## Cleaning Lanarkite specimens are extremely delicate, soft, and brittle. Mechanical cleaning is highly risky. If necessary, compressed air can be used to remove loose dust. Contact with water, especially acids, which can damage it, should be avoided. ## What to Avoid Ultrasonic cleaners, all chemicals (especially acids), high temperatures, and sudden temperature changes should be absolutely avoided. The mineral is sensitive to shocks and impacts. Due to its lead content, inhaling dust should be avoided, and hands should be washed after any contact with the specimen. ## Storage Lanarkite requires storage in stable conditions, away from sources of vibration and dust. It is best kept in a closed display box, lined with soft material. It should not be stored in contact with other, harder minerals that could scratch it.