Painite
Chemical formula: CaZr<sup>4+</sup>Al<sub>9</sub>O<sub>15</sub>(BO<sub>3</sub>)
Painite is an extremely rare borate mineral, known for its intensely red crystals and its status as one of the rarest gemstones on Earth.
Properties
- Mohs hardness
- 8
- Luster
- Vitreous
- Streak
- White
- Density
- 4.01-4.03
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Key diagnostic features of painite are its hexagonal crystal habit (often appearing orthorhombic), high hardness (8 on the Mohs scale), and characteristic density (approx. 4.01 g/cm³). The most unique feature is its very strong pleochroism, manifested by a color change from ruby-red to orangish-brown depending on the viewing angle. Its optical properties, such as refractive indices, are also helpful in identification. ## Distinguishing from Similar Minerals Painite is sometimes confused with ruby, spinel, and some garnets. It is distinguished from ruby by its hexagonal crystallographic system (ruby crystallizes in the trigonal system) and different optical properties. Spinel and garnet crystallize in the isometric system and do not exhibit pleochroism, which is a key distinguishing feature. ## Crystal Forms Painite forms elongated, prismatic crystals with a hexagonal cross-section. They are often terminated by flat pinacoids. Despite hexagonal symmetry, their habit can be pseudo-orthorhombic.
Geological environment
## Genesis Painite forms under conditions of contact metamorphism, in calcium and boron-rich rocks that have been subjected to high temperatures associated with granite intrusions. It primarily crystallizes in skarns. However, most known specimens have been found in alluvial (detrital) deposits, where they arrived as a result of erosion and weathering of parent rocks. ## Mineral Associations This mineral occurs in association with other gemstones and minerals typical of pegmatites and skarns in the Mogok region. The most common associations include corundum (especially its ruby variety), spinel, tourmaline, danburite, and phlogopite. ## Localities For many years, the only confirmed locality for painite was the Mogok region in Myanmar (formerly Burma). To this day, it remains the main and practically sole source of specimens of collectible and gemological significance. New finds, though still very limited, come from several mines in this region, such as Kyauk-pyat-thet, Thurein-taung, and Wet Loo.
Rarity
Extremely rare
For collectors
## Quality Criteria The most highly valued painite specimens are characterized by a deep, saturated, ruby-red color. Transparency and clarity are also crucial – most crystals are heavily fractured or contain inclusions, making clean stones an absolute rarity. Size is another criterion; specimens over several carats are extremely rare. Well-formed, undamaged crystals with sharp edges are sought after by mineral collectors. ## Popular Localities The most prized specimens, both raw crystals and facet-grade material, come from historical and contemporary localities within the Mogok Stone Tract in Myanmar. Specimens from this locality set the standard for quality for this mineral.
Care and storage
## Cleaning Painite is hard, but due to its rarity and potential internal fractures, it requires gentle cleaning. It is best to use a soft brush and lukewarm water with a small amount of mild soap. After washing, it should be thoroughly rinsed with distilled water and allowed to dry completely. ## What to Avoid Although it is scratch-resistant, contact with aggressive chemicals and acids should be avoided. Ultrasonic and steam cleaning are risky and not recommended, as they can lead to the enlargement of existing cracks. Sudden temperature changes should also be avoided. ## Storage Painite specimens, especially those of gemological value, should be stored separately in a padded box or display case. This prevents accidental scratching by harder materials (e.g., diamond) and protects against mechanical damage.