Serendibite

Serendibite
Serendibite, 1.06 - 4.06 ct, Myanmar
General
Category	Inosilicates
Formula (repeating unit)	(Ca,Na)2(Mg,Fe^2+)3(Al,Fe^3+)3[O2|(Si,Al,B)6O18]
Strunz classification	9.DH.40
Dana classification	69.2.1a.6
Crystal system	Triclinic
Identification
Color	pale yellow, blue-green, greyish blue, black
Crystal symmetry	Triclinic - pinacoidal H-M symbol (1) Space group: P1
Twinning	Polysynthetic on {0-11} is common
Cleavage	None Observed
Mohs scale hardness	6.5 - 7
Luster	Vitreous
Streak	White
Diaphaneity	Transparent, Translucent,Opaque
Density	3.42 - 3.52 g/cm^3 (Measured) 3.47 g/cm^3 (Calculated)
Optical properties	Biaxial (+)
Refractive index	1.701 - 1.706
Pleochroism	Visible,strong, color: green, blue, yellow, bluegreen, light yellow
2V angle	Measured: 80° , Calculated: 80°
Dispersion	strong
References	[1][2]

Serendibite is an extremely rare mineral and gem that was first discovered in 1902 in Sri Lanka by Dunil Palitha Gunasekera and named after Serendib, the old Arabic name for Sri Lanka. It is considered one of the rarest gemstones in the world.

Pleochroism

Pleochroism with Serendibite

Most Serendibite gems are opaque, but some have shown gold brown, green and blue colors with transmitted light.

References

1. Serendibite: Serendibite mineral information on Mindat
2. Serendibite mineral data on G-Empire The World of Gems - Die Welt der Edelsteine