Roweite
Chemical formula: Ca<sub>2</sub>Mn<sup>2+</sup><sub>2</sub>B<sub>4</sub>O<sub>7</sub>(OH)<sub>6</sub>
Roweite is a rare calcium manganese borate, forming colorless to light brown, radial aggregates of acicular crystals.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.93
- Cleavage
- Good on {100} and {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Roweite is most easily identified by its characteristic mode of occurrence – radial or spherical aggregates composed of fine, acicular crystals. Its association with minerals from the Franklin deposit (franklinite, willemite, zincite) is a strong diagnostic indicator. Its light color (from colorless to light brown) and vitreous luster are also helpful. ## Distinguishing from Similar Minerals Roweite can be confused with other borates or silicates that form radial aggregates, such as pectolite or natrolite. It differs from pectolite by its lower hardness and different environment of occurrence (pectolite forms in volcanic rocks). From zeolites like natrolite, it differs primarily in genesis – roweite is a product of metamorphism, not hydrothermal processes in gas vesicles. ## Crystal Forms Roweite crystals are elongated along the [001] axis and have an acicular or bladed habit. They almost always occur in radial, spherulitic, or fibrous clusters and aggregates. They rarely form single, well-developed crystals.
Geological environment
## Genesis Roweite is a mineral of metamorphic origin. It forms as a result of contact or regional metamorphism of metamorphosed, stratiform zinc, manganese, and iron ore deposits, embedded in carbonate rocks (marbles). It forms in veins and fractures cutting through these deposits. ## Mineral Associations This mineral co-occurs with many other rare minerals characteristic of the Franklin deposit in New Jersey. Its most common associations include: franklinite, willemite, zincite, andradite, rhodochrosite, barite, as well as other borates such as sussexite and fluoborite. ## Localities The most important and classic locality for roweite, where the best specimens originate, is the Franklin Mine in Sussex County, New Jersey, USA. It is also known from the nearby Sterling Hill deposit. Outside the USA, its presence has been noted in the Kombat Mine in Namibia and in several locations in Sweden (e.g., Långban).
Rarity
Rare
For collectors
## Quality Criteria Most valued by collectors are specimens with well-formed, spherical or radial aggregates with a distinct structure. The size of these aggregates and their contrast with the rock matrix are important. Colorless or pure, light-colored specimens are more desirable than those with a dirty, brownish hue. Association with other rare Franklin minerals, such as franklinite or willemite, is also significant. ## Popular Localities By far the most sought-after and classic roweite specimens come from its type locality – the Franklin Mine in New Jersey, USA. Material from this location is considered exemplary for this species.
Care and storage
## Cleaning Roweite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its brittleness and possible reactivity, wet cleaning, especially with detergents or acids, is not recommended. If liquid is necessary, only distilled water or isopropyl alcohol should be used, applied locally and very gently. ## What to Avoid Avoid contact with chemicals, especially acids, which can damage the mineral. Roweite is brittle, so it must be protected from impacts, falls, and vibrations. It should not be heated or subjected to sudden temperature changes. ## Storage Roweite specimens are best stored in individual, padded collector boxes to prevent abrasions and mechanical damage. They should be kept in stable conditions, away from moisture and direct sunlight, although sunlight does not affect its color.