Cobaltkoritnigite
Chemical formula: Co²⁺(As⁵⁺O₃OH)·H₂O
A rare cobalt arsenate, forming characteristic, violet-pink, bladed crystals, being the cobalt analog of koritnigite.
Properties
- Mohs hardness
- 2-3
- Color
- Pale purple to intense purple, pale rose red to intense purple-rose
- Luster
- Vitreous
- Streak
- Pale pink
- Density
- 0
- Cleavage
- {010} perfect; {100} good.
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Cobaltkoritnigite is primarily identified by its unique, intense violet-pink color, crystal habit (small, bladed or acicular), and characteristic paragenesis. It occurs as small aggregates on host rocks rich in other cobalt and arsenic minerals. ## Distinguishing from Similar Minerals This mineral can be confused with erythrite, which also has a reddish-pink color and occurs in similar environments. However, erythrite typically forms larger, more prismatic crystals and has perfect cleavage in one direction, whereas cobaltkoritnigite forms finer, bladed crystals. Definitive distinction often requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Crystals are bladed, elongated along [100] and flattened parallel to {001}. They usually occur as radial or tangled aggregates, as well as dispersed, individual crystals on the rock matrix.
Geological environment
## Genesis Cobaltkoritnigite is a secondary mineral formed in the oxidation (weathering) zones of ore deposits rich in cobalt and arsenic. It forms under low-temperature conditions as a result of the alteration of primary cobalt sulfides and arsenides. ## Mineral Associations This mineral co-occurs with other secondary arsenic and cobalt minerals. The most common associated minerals are erythrite, pharmacosiderite, goethite, quartz, talmessite, and other rare arsenates such as gersdorffite or cobaltian maghrebiite. ## Localities The most important and type locality for cobaltkoritnigite is the Aghbar mine in the Bou Azzer district, Morocco. This is a world-renowned locality for cobalt-arsenic minerals. Besides Morocco, its presence has also been reported in the Daniel mine near Wittichen in the Black Forest (Germany).
Rarity
Very rare
For collectors
## Quality Criteria The most prized cobaltkoritnigite specimens are characterized by an intense, saturated violet-pink color. Rich clusters of well-formed, lustrous crystals forming radial aggregates on a contrasting rock matrix are highly valued. Crystal size, although usually small, also affects value – specimens with crystals exceeding 1 mm are rare. The absence of damage to the delicate needles is also important. ## Popular Localities Undoubtedly, the best and most sought-after specimens come from the type locality – the Aghbar mine in the Bou Azzer region of Morocco. Specimens from this locality set the standard of quality for this mineral.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its reactivity and softness, contact with water and any chemical agents should be avoided. If liquid is necessary, pure isopropyl alcohol can be used very carefully, applied locally, and allowed to evaporate quickly. ## What to Avoid Contact with water, acids, and other chemicals that can damage or dissolve the mineral must be strictly avoided. It is sensitive to high temperatures and mechanical shocks. It should not be cleaned with ultrasound. Prolonged exposure to strong light may not be advisable, although there are no detailed studies on this topic. ## Storage Cobaltkoritnigite specimens should be stored in stable, dry conditions, away from direct sunlight and heat sources. It is best to store it in a closed display box to protect delicate crystals from mechanical damage and dust.