Colorless Danburite Crystals in Phenakite from Myanmar

Sai Gon Khay and Kyaw Thu

Phenakite (Be₂SiO₄), also known as phenacite, is a rare beryllium silicate mineral characterized primarily by its colorless appearance, although it may also exhibit shades of yellow, pink, or brown. Phenakite is typically found in granitic pegmatite deposits and is recognized from many localities worldwide.

A 4.68 ct colorless faceted oval specimen measuring 10.37 × 9.25 × 7.52 mm sourced from Khetchel, near Momeik in Myanmar, was recently examined by the authors. Based on its physical and optical properties, such as a refractive index of 1.653–1.670 and a specific gravity of 2.97, the mineral was identified as phenakite. Microscopic observation revealed the presence of well-formed prismatic crystal inclusions (see above). These transparent crystals were identified through Raman microanalysis as danburite (CaB₂(SiO₄)₂). Unusual inclusions, such as perettiite-(Y) and tusionite, have been documented in phenakite from Khetchel (Summer 2018 G&G Micro-World, p. 228). To the authors’ knowledge, however, this is the first documented case of danburite inclusions in phenakite.