Marokite
Chemical formula: CaMn<sup>3+</sup><sub>2</sub>O<sub>4</sub>
Marokite is a rare calcium manganese oxide, forming black, metallic-lustered crystals with a tabular or prismatic habit.
Properties
- Mohs hardness
- 6
- Luster
- Metallic
- Streak
- Black
- Density
- 4.64
- Cleavage
- Good on {110}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Key diagnostic features of marokite include its black color, strong metallic luster, relatively high hardness (6 on the Mohs scale), and characteristic crystal shape – tabular or short-prismatic, often with striations. A black streak is also an important clue. ## Distinguishing from Similar Minerals Marokite is sometimes confused with hematite, goethite, or ilmenite. It is distinguished from hematite by its black streak (hematite has a cherry-red streak) and crystal habit. It differs from goethite by its higher hardness and metallic luster (goethite often has a silky or dull luster and a yellowish-brown streak). Distinguishing it from ilmenite can be difficult and often requires advanced studies (e.g., XRD) due to similar physical properties. ## Crystal Forms Marokite crystals crystallize in the orthorhombic system. They most often take the form of flattened tablets or short, thick prisms. Crystal faces are often vertically striated. It also occurs as granular aggregates or as massive inclusions in other minerals.
Geological environment
## Genesis Marokite is a hydrothermal mineral. It forms in low-temperature veins cutting through manganese deposits that have undergone contact metamorphism. It forms in an environment rich in manganese and calcium. ## Mineral Associations This mineral often co-occurs with other manganese minerals. Its most common associations include: hausmannite, braunite, calcite, gaudefroyite, andradite, hematite, and various manganese oxides. ## Localities The most important and classic locality for marokite, from which the world's best specimens originate, is the Tachgagalt manganese deposit, near Ouarzazate (Warzazat) in the Anti-Atlas Mountains in Morocco. It has also been found in the Wessels Mine in Hotazel (Northern Cape Province, South Africa) and the N'Chwaning II Mine in Kuruman, also in South Africa.
Rarity
Rare
For collectors
## Quality Criteria Specimens with sharp, well-formed crystals and a strong, metallic luster are most highly valued by collectors. Single, large crystals or groups of smaller but distinctly formed crystals are highly prized. A contrasting matrix, such as white calcite, enhances its attractiveness. Undamaged specimens with clean, lustrous faces command the highest prices. ## Popular Localities By far the most sought-after and classic marokite specimens come from the type locality – the Tachgagalt deposit in Morocco. Specimens from mines in the Kuruman region of South Africa (Wessels, N'Chwaning) are also valued, although they often have a slightly different crystal habit.
Care and storage
## Cleaning Marokite specimens should only be cleaned mechanically, using a soft, dry brush or paintbrush to remove dust. Compressed air may be used. For more stubborn dirt, a damp (not wet) cloth with distilled water can be used very carefully, immediately drying the specimen. ## What to Avoid Contact with acids and other chemicals that may react with oxides must be strictly avoided. Ultrasonic cleaners should not be used. The mineral is stable, but extreme temperature changes should be avoided. ## Storage Marokite is best stored in closed boxes or display cabinets to protect it from dust and mechanical damage. It does not require special conditions regarding humidity or light, but like any collector's mineral, it should be protected from prolonged, direct exposure to sunlight.