Christelite
Chemical formula: Zn<sup>2+</sup><sub>3</sub>Cu<sup>2+</sup><sub>2</sub>(S<sup>6+</sup><sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>·4H<sub>2</sub>O
Christelite is a very rare, secondary zinc and copper sulfate, forming aggregates of blue, tabular crystals.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous to pearly
- Streak
- Light blue
- Density
- 3.08
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Triclinic
Diagnostic features
## Identification Christelite can be identified by its characteristic pale blue color, its form of thin, tabular crystals forming rosette aggregates, and its occurrence in the oxidation zones of ore deposits. It is very soft and has excellent cleavage. ## Distinguishing from Similar Minerals It can be confused with other secondary copper sulfates, such as ktenasite, serpierite, or linarite. It differs from ktenasite by its crystal habit (ktenasite forms bladed crystals). It is distinguished from linarite by its lighter color and lower hardness. Accurate identification almost always requires advanced analytical methods, such as XRD or EDS. ## Crystal Forms Crystals are thin, tabular, with a hexagonal outline. They most often occur as rosette-like, radial, or randomly oriented aggregates, as well as thin crusts on the host rock.
Geological environment
## Genesis Christelite is a secondary mineral, forming in the oxidation zones (gossans) of polymetallic ore deposits rich in zinc sulfides (sphalerite) and copper (chalcopyrite). It forms under low-temperature conditions as a result of the weathering of primary ore minerals. ## Mineral Associations It most often co-occurs with other secondary zinc and copper minerals. At the type locality (Christiana Levin mine, Germany), it was found in association with gypsum, hemimorphite, ktenasite, serpierite, and brochantite. In other localities, it is accompanied by, among others, sphalerite, chalcopyrite, galena, anglesite, and linarite. ## Localities The most important occurrences of this very rare mineral are: * Germany - Christiana Levin mine in Essen, North Rhine-Westphalia (type locality). * Greece - mines in the Laurion region (Kamariza, Sounion). * United Kingdom - Red Gill mine in Caldbeck Fells, Cumbria, England. * USA - Blue Bell mine in San Bernardino County, California.
Rarity
Very rare
For collectors
## Quality Criteria The most prized christelite specimens are those with well-formed, distinct rosettes or rich crusts of intense blue color. Contrast with the host rock and the absence of damage to delicate crystals are important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. Co-occurrence with other rare secondary minerals increases the value of the specimen. ## Popular Localities Specimens from the type locality in Germany and from Greek Laurion are the most well-known in collections. Material from California and England is also sought after but appears on the market even less frequently.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Any contact with water, even distilled, is highly risky and can lead to the dissolution or damage of delicate crystals. Ultrasonic cleaners and any chemical agents should be avoided. ## What to Avoid Contact with water and other liquids must be absolutely avoided. The mineral is sensitive to high temperatures and direct sunlight, which can cause dehydration and color change. It is very soft and brittle, susceptible to mechanical damage. ## Storage It is recommended to store specimens in tightly sealed, stable containers (e.g., "perky box" type) to protect them from dust, moisture, and physical damage. They should ideally be kept in a dry place with a constant temperature.