Teruggite
Chemical formula: Ca<sub>4</sub>Mg[As<sup>5+</sup>B<sub>6</sub>O<sub>11</sub>(OH)<sub>6</sub>]<sub>2</sub>·14H<sub>2</sub>O
Teruggite is a rare, hydrated calcium magnesium arsenate-borate, forming colorless or white, tabular crystals.
Properties
- Mohs hardness
- 3
- Luster
- Pearly, Vitreous
- Streak
- White
- Density
- 2.31
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of teruggite include its habit (small, tabular crystals in radial aggregates), pearly luster on cleavage surfaces, low hardness, and occurrence in a specific evaporitic environment. It is a very rare mineral, which is also an important clue. ## Distinguishing from Similar Minerals It can be confused with other borates or sulfates found in similar environments, such as gypsum or colemanite. It differs from gypsum by its slightly greater hardness and different crystal form. It differs from colemanite by its chemical composition (presence of arsenic) and crystallographic properties, which require advanced research methods for definitive confirmation. ## Crystal Forms Teruggite crystals are tabular or bladed, elongated in one direction. They usually form fan-shaped, radial, or spherulitic aggregates. They rarely occur as single, well-formed crystals.
Geological environment
## Genesis Teruggite is a sedimentary mineral. It forms as a result of evaporation of saline lakes in a dry and desert climate. It crystallizes from solutions rich in boron, arsenic, calcium, and magnesium. ## Mineral Associations This mineral co-occurs with other borates and salts characteristic of evaporitic environments. In its type locality (Loma Blanca, Argentina), it was found in association with inyoite, meyerhofferite, colemanite, hydroboracite, ulexite, as well as gypsum and calcite. ## Localities The most important and classic occurrence of teruggite is its type locality: the Loma Blanca borate deposit, near Coranzuli in Jujuy Province, Argentina. This is the only confirmed and well-documented locality for this mineral in the world.
Rarity
Extremely rare
For collectors
## Quality Criteria As an extremely rare mineral, every teruggite specimen is valuable to advanced collectors of rare and systematic minerals. The most desirable specimens are those with well-formed, visible crystals forming aesthetic, radial aggregates on a rock matrix. The size of the aggregates and the absence of damage significantly increase the value of the specimen. ## Popular Localities The only source of collectible specimens is the Loma Blanca deposit in Argentina. Specimens from this locality are the standard for the species.
Care and storage
## Cleaning Due to its softness and perfect cleavage, teruggite should be handled with great care. Compressed air or a very soft brush is best for removing dust. Wet cleaning, especially with detergents, should be avoided. ## What to Avoid Avoid contact with water and chemicals, which can damage the delicate crystals. The mineral is sensitive to ultrasound and mechanical shocks. It should not be heated or exposed to acids. ## Storage Teruggite specimens should be stored in stable conditions, in separate, padded boxes, to prevent mechanical damage and contact with harder minerals. It is best to protect it from dust and moisture.