Scapolite
Scapolite is a gemstone belonging to a solid solution group formed by the continuous mixture of meionite and marialite. In ancient times, yellow to colorless crystals may have been confused with topaz. Gem-quality crystals are produced in limited locations such as Mogok in Myanmar, Sri Lanka, Tanzania, and Madagascar. They possess a rich color variation, including colorless, yellow, purple, and pink, with rare pink varieties and stones exhibiting a cat's-eye effect being high-end items for collectors.
Scapolite with its appealing soft hues and cat's-eye effect
Basic Information
| English Name | Scapolite |
|---|---|
| Japanese Name | Chuuseki |
| Chemical Composition | Solid solution of Marialite: Na₄Cl[Al₃(Si₃O₈)₃] / Meionite: Ca₄[CO₃|(Al₂Si₂O₈)₃] |
| Crystal System | Tetragonal |
| Hardness | 5.5–6 |
| Specific Gravity | Approx. 2.65 |
Characteristics and Varieties
The scapolite series consists of a solid solution in which the composition changes continuously: Meionite → Dipyre → Wernerite → Marialite.
- Scapolite Cat's-Eye: In stones with many tubular inclusions (fine tube-like internal inclusions), a chatoyancy effect resembling a cat's eye appears.
- Star Scapolite: Types that reveal four- or six-rayed stars depending on the arrangement of inclusions are also known.
- Rare Colors: Colorless and pink stones are rarely produced; especially pink cat's-eye stones are traded at very high prices.
- New Variety: A type containing high amounts of sulfate groups (SO₄) has been reported and named "Silvialite."
Trade Names, Treatments, and Similar Stones
Pink scapolite found in Myanmar in 1913 was initially thought to be moonstone and was traded under names such as "pink moonstone" and "rose moonstone."
Irradiation treatment is sometimes performed to achieve a black color, and it is said that cat's-eye quality rough stones are often used for this purpose. Irradiated stones have an appearance very similar to blackish moonstone.
Colorless, yellow, and purple stones look close to quartz or amethyst, making visual identification almost impossible. The property of fluorescing red under short-wave ultraviolet light (300–200 nm) serves as a major clue for identifying scapolites.
Handling Tips: It is easy to confuse with quartz or moonstone based on appearance alone, and purple stones in particular have a refractive index and specific gravity close to amethyst, which can lead to misidentification without professional measurement. We recommend checking an identification report when purchasing high-value items like pink cat's-eye.