Dravite

Chemical formula: NaMg₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃OH

Dravite is a mineral from the tourmaline group, characterized by variable color, from light brown to black, often found in metamorphic rocks.

## Characteristics Dravite is a mineral belonging to the tourmaline group, a borosilicate of aluminum. It typically occurs as elongated, striated crystals with a triangular or hexagonal cross-section. Its appearance can vary, from transparent, light brown forms to opaque, dark brown or black specimens. It often forms radial or columnar aggregates. ## Physical Properties Dravite is characterized by a hardness of 7 on the Mohs scale. It has a vitreous to greasy luster. The transparency of dravite ranges from transparent to translucent. Its density is approximately 3.03 g/cm³. ## Colors and Varieties The color of dravite is variable and includes shades from light brown to dark brown, and even brownish-black. It can also occur in dark yellow or blue. Differences in color result from the presence of trace element impurities in its crystal structure. ## History and Name The name dravite comes from the Drava River in Austria, where this mineral was first described in 1883. It is one of many minerals from the tourmaline group that have been named after their discovery location or a characteristic feature. ## Uses Dravite, like other tourmalines, is primarily used in jewelry, especially its transparent and well-colored varieties. High-quality specimens are valued by mineral collectors.

Properties

Mohs hardness: 7
Luster: Vitreous to oily.
Streak: Light brown, rarely white.
Density: 3.03
Cleavage: Very poor <mi>{11_20} {10_11}</mi>
Fracture: Nierówny
Transparency: Transparent,Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Dravite can be identified by its typical columnar habit or striated crystals, as well as its hardness of 7 on the Mohs scale. The variable color, from brown to black, is also characteristic. A vitreous to greasy luster is also a diagnostic feature. ## Distinguishing from Similar Minerals Dravite can be confused with other tourmalines, such as schorl, but it differs from them in chemical composition and often in color. It is distinguished from garnets by its crystal habit and lack of cleavage. It is distinguished from some amphiboles by its hardness and the absence of characteristic amphibole cleavage. ## Crystal Forms Dravite most often forms elongated, columnar crystals with a triangular or hexagonal cross-section. Crystal surfaces are often distinctly striated parallel to the c-axis. It can also occur as massive, radial, or granular aggregates.

Geological environment

## Genesis Dravite forms in metamorphic rocks, especially in marbles and crystalline schists, where it is a product of boron metasomatism. It can also occur in pegmatites and boron-rich igneous rocks. ## Mineral Associations Dravite often co-occurs with quartz, feldspar, muscovite, biotite, calcite, dolomite, as well as other tourmalines and boron minerals. ## Localities Known dravite localities include Austria (Drava River area), Brazil, Russia (Urals), Canada, USA (California, New York), Tanzania, and Madagascar.

Rarity

Common

For collectors

## Quality Criteria The most prized dravite specimens are those with well-formed, transparent or translucent crystals, intense and uniform coloration, and without visible inclusions or cracks. Large, aesthetic crystal aggregates are also highly sought after. ## Popular Localities Particularly valued specimens come from Brazil, Tanzania, and Madagascar, where high-quality gem-grade crystals are found. Specimens from Austria have historical significance.

Care and storage

## Cleaning Dravite can be cleaned with a soft brush and lukewarm water with mild soap. Strong chemical agents that can damage the mineral's surface should be avoided. ## What to Avoid This mineral is sensitive to sudden temperature changes, which can lead to cracks. Prolonged exposure to direct sunlight, which can affect color intensity, should be avoided. Contact with acids and strong bases is not recommended. ## Storage Dravite is best stored in separate boxes or pouches to prevent scratching by harder minerals. Ideal conditions include stable temperature and moderate humidity. Storing it in a dark place will help preserve its color.