Ertlite
Chemical formula: NaAl₃Al₆(Si₄B₂O₁₈)(BO₃)₃(OH)₃O
Ertlite is a newly discovered, very rare mineral from the tourmaline group, distinguished by its unique chemical composition and high hardness.
Properties
- Mohs hardness
- 7-8
- Luster
- Vitreous
- Streak
- white
- Density
- 3.128
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Transparent
- Crystal system
- Trigonal
Diagnostic features
## Identification The key diagnostic feature of ertlite is its belonging to the tourmaline group combined with its unique chemical composition (dominance of Na and Al). In practice, without advanced analyses (e.g., EDS/WDS), its identification is extremely difficult. Clues may include: high hardness (7-8), vitreous luster, trigonal crystal form, and occurrence in a specific geological environment. Strong pleochroism is also an important optical feature. ## Distinguishing from similar minerals Ertlite is visually almost impossible to distinguish from other colorless, pink, or yellowish tourmalines, such as elbaite, rossmanite, or liddicoatite, without specialized studies. The geological context and associated minerals may provide some indication, but definitive confirmation requires chemical analysis. ## Crystal forms Ertlite forms prismatic, elongated crystals, typical of tourmalines. The crystals are terminated by trigonal pyramid faces and often exhibit vertical striations on the prism faces. It occurs as single, well-formed crystals.
Geological environment
## Genesis Ertlite forms in lithium- and boron-rich granitic pegmatites. These are geologically complex environments where, in the late stages of magma crystallization, rare elements concentrate, enabling the formation of unique minerals. Its presence indicates highly specific chemical conditions prevailing in the pegmatite. ## Mineral associations This mineral co-occurs with other minerals typical of lithium pegmatites. In the type locality in Madagascar, it was found in association with quartz, feldspars (albite), liddicoatite, rossmanite, and lepidolite. In Myanmar, it is accompanied by calcite, feldspar, and other tourmalines. ## Localities Confirmed occurrences of ertlite, which are also its type localities, are the Sahatany Valley in the Vakinankaratra region of Madagascar and the Mogok region in Myanmar. These are world-renowned pegmatite areas, known for supplying many valuable minerals and gemstones.
Rarity
Extremely rare
For collectors
## Quality criteria As a newly described and extremely rare mineral, every authenticated specimen of ertlite is extremely valuable to collectors specializing in mineral systematics or the tourmaline group. Specimens with well-formed, sharp crystals, good transparency, and intense, pure color (especially pink) will be most highly prized. The presence of the mineral on a rock matrix, in association with other minerals from the given locality, is also important. ## Popular localities Both known localities – the Sahatany Valley in Madagascar and Mogok in Myanmar – are the source of the most sought-after specimens, as they are the type localities for this mineral. Specimens from these localities have the highest scientific and collector value.
Care and storage
## Cleaning Ertlite, as a hard and chemically stable mineral, can be safely cleaned with lukewarm water and a mild soap, using a soft brush. After washing, it should be thoroughly rinsed, preferably with distilled water, and left to dry completely. ## What to avoid Despite its high hardness, contact with strong acids, especially hydrofluoric acid, which can damage its surface, should be avoided. It should also be protected from sudden temperature changes (thermal shock) and strong impacts, which can cause fractures along internal cleavages. ## Storage Ertlite specimens are best stored in separate, padded boxes or on stands to prevent scratching by harder minerals (e.g., diamond) or scratching softer minerals. Due to its transparency and color, it does not require special protection from light.