Yangite

Yangite (PbMnSi₃O₈·H₂O) is a chain-silicate mineral, first discovered within the Kombat mine in Namibia. The mineral is named after Hexiong Yang, a researcher at the University of Arizona's Department of Geosciences. Yangite was approved as a valid mineral species by the International Mineralogical Association in 2012.

Yangite
General
Category	chain silicate
Formula (repeating unit)	PbMnSi3O8•H2O
IMA symbol	Ygi
Crystal system	triclinic
Crystal class	pinacoidal
Unit cell	a = 9.6015(9) Å, b = 7.2712(7) Å, c = 7.9833(8) Å α = 105.910(4)°, β = 118.229(4)°, γ = 109.938(5)°
Identification
Color	colorless to pale brown
Crystal habit	bladed or platy
Twinning	not observed
Cleavage	perfect on {101}
Tenacity	sectile
Mohs scale hardness	5
Luster	vitreous
Streak	white
Specific gravity	4.14 g/cm3 (measured) 4.16 g/cm3 (calculated)
Birefringence	δ = 0.015
2V angle	77° (measured)
Solubility	insoluble in water, acetone, or hydrochloric acid
References

Occurrence

Yangite was initially found within a specimen taken from the Kombat mine, located in the Otavi Valley, Namibia. The specimen was obtained from John Innes, a senior mineralogist of the Tsumeb Corporation. Yangite occurs in an ore defined as an epithermal association. This ore type forms with narrow veins composed of galena, rhodochrosite, helvite, and barite.

Physical Properties

Yangite is colorless, ranging to pale brown when exposed to transmitted light. The mineral has a vitreous luster and streaks white. Yangite maintains a Mohs hardness of five, and demonstrates perfect cleavage along {101}. There is no evidence of twinning or parting within the available specimens. Yangite is sectile, commonly found with bladed or platy habit. The mineral is biaxial, elongated up to 12 mm in length along the [010] axis. Yangite is insoluble in several fluids, including water, acetone, and hydrochloric acid.

Chemical composition

Yangite has a consistent chemical composition, determined using a CAMECA SX100 electron microprobe. Additionally, the presence of H₂O was confirmed using structural determination and Raman spectroscopic measurements.

Elemental Weight Percent:

element	wt%
Pb	42.08
O	29.24
Si	17.11
Mn	11.16
H	00.41
Total	100.0

X-ray crystallography

Yangite was analyzed by both powder and single-crystal X-ray diffraction. Data was collected using the Bruker X8 APEX2 CCD diffractometer. The diffraction data was influenced by severe peak overlap, leading to uncertainty in the resulting index.

Powder Diffraction Data:

d-spacing	intensity
7.379 Å	100
6.648 Å	48
3.717 Å	44
3.517 Å	38
2.992 Å	38
2.949 Å	40
2.917 Å	65
2.907 Å	55

Crystal structure

The chain silicate structure is formed by double wollastonite chains. These tetrahedral formations run parallel with the [010] axis and connect with Mn-polyhedra and Pb-polyhedra at the corners. The chains are also defined by four-membered and six-membered alternating tetrahedral rings. Yangite has three Si tetrahedral sites, defined as Si1, Si2, and Si3. Respectively, the average bond lengths are 1.622 Å, 1.622 Å, and 1.624 Å. Yangite is composed of an octahedrally coordinated Mn²⁺ cation. Within the crystal structure, Pb²⁺ has a coordination number of five, bonded with O molecules.

See also

• List of minerals