Gugiaite
Gugiaite is a melilite mineral, named for the Chinese village of Gugia where it was first discovered. Its chemical formula is Ca2BeSi2O7. It occurs mostly in skarns with melanite adjacent to an alkali syenite and has no economic value. Its crystals are small tetragonal tablets with vitreous luster and perfect cleavage. It is colorless and transparent with a density of three. The mineral belongs to space group P-421m and is strongly piezoelectric.
| Gugiaite | |
|---|---|
| General | |
| Category | Sorosilicate |
| Formula (repeating unit) | Ca2[BeSi2O7] |
| IMA symbol | Gug |
| Strunz classification | 9.BB.10 |
| Dana classification | 55.04.02.06 |
| Crystal system | Tetragonal |
| Crystal class | Scalenohedral (42m) H-M symbol: (4 2m) |
| Space group | P421m |
| Unit cell | a = 7.43, c = 5.024 [Å]; Z = 2 |
| Identification | |
| Color | Colorless |
| Cleavage | Perfect on {010}, distinct {001}, indistinct on {110} |
| Fracture | Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern |
| Mohs scale hardness | 5 |
| Luster | Vitreous, glassy |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 3.03 |
| Optical properties | uniaxial (+) |
| Refractive index | nω = 1.664 nε = 1.672 |
| Birefringence | δ = 0.008 |
| Other characteristics | strongly piezoelectric |
| References | |
Shortly after the discovery of gugiaite, it was noted that a new name was unnecessary as it could have been considered an end member of meliphanite, (Ca,Na)2Be(Si,Al)2(O,F)2 differing mainly in containing much less Na and F (Fleischer 1963). Recent data have confirmed that gugiaite differs from meliphanite optically and structurally (Grice and Hawthorne 2002). Gugiaite is a melilite and is distinctly different from other beryllium minerals such as meliphanite and leucophanite (Grice and Hawthorne 2002). Gugiaite is named for its locality near the village of Gugia, China (Peng et al. 1962). Incongruent information exists regarding Gugia; consequently the actual location of this village within China is unclear (de Fourestier 2005). Gujia is most often referenced as being in either Jiangsu Province or Liaoning Province (Yang et al. 2001; Mandarino 2005).