YUANJIANGITE
The yuanjiangite is a mineral found in the sandy bottom of the river Yuanjiang, near the town of Yuanlin , province of Hunan in China. The name comes from a place of discovery. Occurs in hexagonal prisms and anhedral grains.

Chemical Composition

Chemical Formula:	AuSn
Composition:	Molecular Weight = 315.68 gm     Tin 37.60 % Sn     Gold 62.40 % Au
Environment:	Placer deposit.
Locality:	In sandy gravel in the middle course of the Yuanjiang     River, near the town of Yuanlin, Hunan Province,     Peoples Republic of China
Name Origin:	Named after its locality.

Crystallography

Axial Ratios:	a:c = 1:1.27664
Cell Dimensions:	a = 4.316, c = 5.51, Z = 2; V = 88.89 Den(Calc)= 11.79
Crystal System:	Hexagonal - Dihexagonal DipyramidalH-M Symbol (6/m)     Space Group: P
X Ray Diffraction:	By Intensity(I/Io): 2.218(1), 2.159(0.57), 3.087(0.38)

Image

Golden brown crystals of tetra-auricupride on matrix. Image Source: R.Weller/Cochise College

HUNCHUNITE
Hunchunite was discovered in 1992 near the Sandaogou gold field in the vicinity of Hunchun in the province of Jilin in the Republic of China. It is after the Hunchun River where the name is derived. It is often associated with lead, anyuiit, pyrite , pyrrhotite , magnetite and ilmenite.

Chemical Composition

Chemical Formula:	(Au,Ag)2Pb
Composition:	Molecular Weight = 556.58 gm     Silver 9.69 % Ag     Lead 37.23 % Pb     Gold 53.08 % Au
Environment:	Placer deposit.
Locality:	Hunchun River, Jilin province.
Name Origin:	Named after its locality.

Crystallography

Axial Ratios:	a:c =
Cell Dimensions:	a = 7.933, Z = 8; V = 499.24 Den(Calc)= 14.81
Crystal System:	Isometric - HexoctahedralH-M Symbol (4/m 3 2/m)     Space Group: F d3m
X Ray Diffraction:	By Intensity(I/Io): 2.391(1), 2.81(0.3), 1.196(0.26)

Image

Bluish-gray hunchunite in a polished section in reflected light. Image Source: R.Weller/Cochise College

GALENA
Galena is the natural mineral form of lead(II) sulfide. It is the most important lead ore mineral. Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often associated with the minerals sphalerite, calcite and fluorite. Galena deposits are found worldwide in various environments.

Chemical Composition

Chemical Formula:	PbS
Composition:	Molecular Weight = 239.27 gm     Lead 86.60 % Pb     Sulfur 13.40 % S
Environment:	Lead sulfide ore veins, and disseminated in igneous     and sedimentary rocks.
Locality:	Joplin district of Missouri, Kansas, and Oklahoma     and other world wide occurrences.
Name Origin:	The Roman naturalist, Pliny, used the name galena     to describe lead ore.

Crystallography

Axial Ratios:	a:b:c =
Cell Dimensions:	a = 5.936, Z = 4; V = 209.16 Den(Calc)= 7.60
Crystal System:	Isometric - HexoctahedralH-M Symbol (4/m 3 2/m)     Space Group: F m3m
X Ray Diffraction:	By Intensity(I/Io): 2.969(1), 3.429(0.84), 2.099(0.57)

Image

Galena cubic crystal. Image Source: R.Weller/Cochise College

ARGENTITE
It occurs in mineral veins, and when found in large masses, as in is Mexico and in the Comstock Lode in Nevada, it forms an important ore of silver. The mineral was mentioned in 1529, but the name argentite (from the Lat. argentum, silver) was not used till 1845. Old names for the species are Glaserz, silver-glance and vitreous silver.

Chemical Composition

Chemical Formula:	Ag2S
Composition:	Molecular Weight = 247.80 gm     Silver 87.06 % Ag     Sulfur 12.94 % S
Environment:	Low temperature ore veins.
Locality:	Mexico, Saxony, Great Britain and Kongsberg, Norway     are notable localities.
Name Origin:	After the Latin, argentum, meaning "silver".

Crystallography

Axial Ratios:	a:b:c =1.7321:1:1.6318
Cell Dimensions:	a = 4.89, Z = 2; V = 116.93 Den(Calc)= 7.04
Crystal System:	Isometric - HexoctahedralH-M Symbol (4/m 3 2/m)     Space Group: | m3m
X Ray Diffraction:	By Intensity(I/Io): 3.351(1), 2.644(0.81), 1.765(0.63).

Image

Argentite crystals. Mexico. Image Source: R.Weller/Cochise College

CHLORARGYRITE
It occurs in mineral veins, and when found in large masses, as in is Mexico and in the Comstock Lode in Nevada, it forms an important ore of silver. The mineral was mentioned in 1529, but the name argentite (from the Lat. argentum, silver) was not used till 1845. Old names for the species are Glaserz, silver-glance and vitreous silver.

Chemical Composition

Chemical Formula:	AgCl
Composition:	Molecular Weight = 143.32 gm     Silver 75.26 % Ag 80.85 % Ag2O     Chlorine 24.74 % Cl 24.74 % Cl
Environment:	Oxidized portions of silver deposits.
Locality:	Broken Hill district, New South Wales, Australia,     are notable localities.
Name Origin:	Named after its chemical composition of chlorine (Greek,     chloros = "pale green") and silver (Latin, argentum).

Crystallography

Axial Ratios:	a:b:c =
Cell Dimensions:	a = 5.556, Z = 4; V = 171.51 Den(Calc)= 5.55
Crystal System:	Isometric - HexoctahedralH-M Symbol (4/m 3 2/m)     Space Group: F m3m
X Ray Diffraction:	By Intensity(I/Io): 2.774(1), 1.962(0.5), 3.2(0.5)

Image

Butterscotch colored cubic crystals of chlorargyrite (Synonym: Cerargyrite) on malachite. Image Source: R.Weller/Cochise College