Herbertsmithite

Herbertsmithite

Herbertsmithite from Caracoles, Sierra Gorda District, Tocopilla Province, Chile. Size: 4.5 x 4.4 x 2.7 cm.
General
Category Halide mineral
Formula
(repeating unit)		 ZnCu3(OH)6Cl2
Strunz classification 3.DA.10c
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3m
Unit cell a = 6.834 Å
c = 14.075 Å; Z = 3
Identification
Color Light green, blue-green
Crystal habit Aggregates of rhombohedral crystals
Cleavage Good on {1011}
Tenacity Brittle
Mohs scale hardness 3–3.5
Luster Vitreous to adamantine
Streak Light green
Diaphaneity Transparent
Specific gravity 3.75-3.95
Optical properties Uniaxial (-)
Refractive index nε 1.817, nω 1.825
Birefringence 0.0080
References [1][2]

Herbertsmithite is a mineral with chemical structure ZnCu3(OH)6Cl2. It is named after the mineralogist Herbert Smith (1872–1953) and was first found in 1972 in Chile. It is polymorphous with kapellasite and closely related to paratacamite. Herbertsmithite is generally found in and around Anarak, Iran, hence its other name, anarakite.

Herbertsmithite is associated with copper mineralizations in syenitic porphyries and granites in Chile and in Triassic dolomite formations in Iran. It has also been reported from the Osborn District in the Big Horn Mountains of Maricopa County, Arizona and the Lavrion District Mines of Attica, Greece.[1]

Herbertsmithite has a vitreous luster and is fairly transparent with a light-green to blue green color. Herbertsmithite has a Mohs hardness of between 3 and 3.5 and is known to have a brittle tenacity. The crystal's density has been calculated at 3.76 g/cm3.

Herbertsmithite, in a pure synthetic form, was discovered in 2012 to be able to exhibit the properties of a quantum spin liquid, a generalized form of strongly correlated quantum spin liquid due to its Kagome lattice structure.[3] Herbertsmithite is the first mineral known to exhibit this unique state of magnetism: it is neither a ferromagnet with mostly aligned magnetic particles, nor is it an antiferromagnet with mostly opposed adjacent magnetic particles; rather its magnetic particles have constantly fluctuating scattered orientations.

Optical conductivity observations[4] suggest the magnetic state in herbertsmithite is a type of emergent gauge field of a gapless U(1) Dirac spin liquid. Other experiments [5] and numerical calculations suggest it is a Z2 spin liquid (or has a Z2 topological order).

References

  1. 1 2 Herbertsmithite at mindat.org
  2. ↑ "Information on Herbertsmithite on Webmineral". Webmineral.com. Retrieved 2013-03-06.
  3. ↑ "MIT researchers discover a new kind of magnetism". Web.mit.edu. 2012-12-19. Retrieved 2013-03-06.
  4. ↑ Pilon; et al. (2013). "Spin-Induced Optical Conductivity in the Spin-Liquid Candidate Herbertsmithite". Physical Review Letters. 111 (12). doi:10.1103/PhysRevLett.111.127401.
  5. ↑ T.-H. Han, J. S. Helton, S. Chu, D. G. Nocera, J. A. Rodriguez-Rivera, C. Broholm, and Y. S. Lee, Nature 492, 406 (2012); M. Fu, T. Imai, T.-H. Han, and Y. S. Lee, Science 350, 655 (2015); T.-H. Han, M. R. Norman, J.-J. Wen, J. A. Rodriguez- Rivera, J. S. Helton, C. Broholm, and Y. S. Lee, Phys. Rev. B 94, 060409 (2016).
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