Sugilite

Sugilite (/ˈsɡɪlt/ SOO-gi-lyt) is a relatively rare pink to purple cyclosilicate mineral with the complex chemical formula KNa2(Fe, Mn, Al)2Li3Si12O30. Sugilite crystallizes in the hexagonal system with prismatic crystals. The crystals are rarely found and the form is usually massive. It has a Mohs hardness of 5.5 to 6.5 and a specific gravity of 2.75 to 2.80. It is mostly translucent.

Sugilite
Smithsonian Exhibit Stone.jpg
16kg Manganoan Sugilite, GIA Laboratory Certified, Smithsonian Exhibition Stone, I.Kurgan Royal Azel, Hall of Gems Smithsonian Museum 1981, Wessels Mine in Northern Cape Province, South Africa
General
CategoryCyclosilicate
Formula
(repeating unit)
KNa2(Fe,Mn,Al)2Li3Si12O30
Strunz classification9.CM.05
Dana classification63.02.01a.09
Crystal systemHexagonal
Crystal classDihexagonal dipyramidal (6/mmm)
H-M symbol: (6/m 2/m 2/m)
Space groupP6/mcc
Unit cella = 10, c = 14 [Å]; Z = 2
Identification
ColorLight brownish-yellow, purple, violet, reddish violet, pale pink, colorless
Crystal habitPrismatic crystals, typically granular to massive
CleavagePoor on {0001}
Mohs scale hardness6–​6 12
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.74
Optical propertiesUniaxial (-)
Refractive indexnω = 1.610 nε = 1.607
Birefringenceδ = 0.003
PleochroismWeak
References[1][2][3]

Sugilite was first described in 1944 by the Japanese petrologist Ken-ichi Sugi (1901–1948) for an occurrence on Iwagi Islet, Japan, where it is found in an aegirine syenite intrusive stock. It is found in a similar environment at Mont Saint-Hilaire, Quebec, Canada. In the Wessels mine in Northern Cape Province of South Africa, sugilite is mined from a strata-bound manganese deposit. It is also reported from Liguria and Tuscany, Italy; New South Wales, Australia and Madhya Pradesh, India.[3]

Note: The mineral is commonly pronounced with a soft "g", as in "ginger". However, as with most minerals, its pronunciation is intended to be the same as the person it is named after; in this case, the Japanese name Sugi has a hard "g", as in "geese".[4]

The mineral is also referred to as lavulite, luvulite, and royal azel by gem and mineral collectors.[2]

Sugilite on Matrix, Wessels Mine in Northern Cape Province, South Africa, size: 2.4 x 2.1 x 1.2 cm

See alsoEdit

ReferencesEdit

  1. ^ Sugilite data on Webmineral
  2. ^ a b Sugilite on Mindat.org
  3. ^ a b Sugilite in the Handbook of Mineralogy
  4. ^ "OpenLearn Live: 8th September 2015 - Meet The Minerals". OpenLearn. The Open University. Retrieved 20 January 2016.

External linksEdit