Chlorophoenicite
Chemical formula: (Mn²⁺,Mg,Zn²⁺)₃Zn²⁺₂As⁵⁺O₄(OH,O)₆
Chlorophenicite is a rare zinc and manganese arsenate, forming acicular crystals with a characteristic green color and silky luster.
Properties
- Mohs hardness
- 3-3.5
- Color
- Usually colorless to white, also light gray-green (natural light); pink to light purplish red (strong artificial light)
- Luster
- Pearly, Silky
- Streak
- Colorless
- Density
- 3.46
- Cleavage
- On {100}, good.
- Fracture
- Splintery
- Transparency
- Transparent,Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Chlorophenicite is most easily recognized by its characteristic grass-green color, silky luster, and typical occurrence in radial or fibrous aggregates. Perfect cleavage in one direction is also an important diagnostic feature. The reaction to heating (color change to red) is a confirming test, but it is destructive to the sample. ## Distinguishing from Similar Minerals This mineral is sometimes confused with other secondary minerals of the oxidation zone, such as annabergite or conichalcite. Annabergite has a similar green color but is a nickel arsenate and occurs in different mineral associations. Conichalcite, a copper and calcium arsenate, more often forms botryoidal or reniform aggregates and usually has a more yellowish shade of green. Accurate differentiation often requires chemical analysis. ## Crystal Forms Chlorophenicite crystals are monoclinic, forming elongated, acicular or bladed prisms. They most often create radial, stellate, or fibrous aggregates. Single, well-formed crystals are less common.
Geological environment
## Genesis Chlorophenicite is a secondary hydrothermal mineral, forming in the oxidation zones of zinc and manganese deposits that have undergone metamorphic processes. It forms in veins and fractures cutting through franklinite and willemite deposits. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Franklin-Sterling Hill deposit. It is most often associated with calcite, willemite, franklinite, zincite, as well as other arsenates like adelite or allaktite. ## Localities The most important and historical locality for chlorophenicite is its type locality - the Franklin deposit and the adjacent Sterling Hill Mine in New Jersey, USA. The best and largest specimens of this mineral come from there. Outside the USA, its presence has been noted in small quantities in the Långban mine in Sweden and in mines in the Vareš region in Bosnia and Herzegovina.
Rarity
Rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, radial aggregates of an intense, grass-green color. Contrast with the host rock (matrix), for example, white calcite, is important. The size of the aggregates and the absence of mechanical damage significantly increase the value of the specimen. Specimens with well-defined, individual crystals, though rarer, are also highly prized. ## Popular Localities By far the most desirable and classic source of chlorophenicite specimens is the Franklin-Sterling Hill complex in New Jersey, USA. Specimens from this locality are considered exemplary for this mineral species.
Care and storage
## Cleaning Chlorophenicite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and perfect cleavage, ultrasonic cleaners and mechanical cleaning should be avoided. If liquid is necessary, only distilled water is recommended, followed by immediate, gentle drying of the specimen. ## What to Avoid The mineral is sensitive to acids and other chemicals. Contact with any household cleaning agents should be avoided. It must be protected from high temperatures, which can cause color change and structural damage. Prolonged exposure to strong sunlight is not advisable. ## Storage Chlorophenicite is brittle and soft, so it should be stored in a separate, padded display box to prevent scratching by harder minerals. It should not be stored in humid conditions. It is best displayed in a closed cabinet, protecting it from dust and mechanical damage.