ANILITE
Discovered in a drusy quartz vein (Ani mine, Japan). It has been approved by IMA in 1968. It is also found at Neudorf, Harz, Germany. The name originated from the Ani mine in Japan.

Chemical Composition

Chemical Formula:	Cu7S4
Composition:	Molecular Weight = 573.09 gm     Copper 77.62 % Cu     Sulfur 22.38 % S
Environment:	In a drusy quartz vein (Ani mine, Japan).
Locality:	Ani mine, Akita Prefecture, Japan; At Neudorf, Harz,     Germany are notable localities.
Name Origin:	For the Ani mine, Japan.

Crystallography

Axial Ratios:	a:b:c =1.0063:1:1.4043
Cell Dimensions:	a = 7.89, b = 7.84, c = 11.01, Z = 4; V = 681.05     Den(Calc)= 5.59
Crystal System:	Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m)     Space Group: P nma
X Ray Diffraction:	By Intensity(I/Io): 1.96(1), 2.77(0.65), 3.2(0.57)

Image

Anilite crystals. Japan. Image Source: R.Weller/Cochise College

CUPRITE
It is a secondary mineral which forms in the oxidized zone of copper sulfide deposits. It frequently occurs in association with native copper, azurite, chrysocolla, malachite, tenorite and a variety of iron oxide minerals. Cuprite was first described in 1845 and the name derives from the Latin "cuprum" for its copper content.

Chemical Composition

Chemical Formula:	Cu2O
Composition:	Molecular Weight = 143.09 gm     Copper 88.82 % Cu 100.00 % Cu2O     Oxygen 11.18 % O
Environment:	Oxidized zone of copper deposits.
Locality:	Commonly in the copper deposits of USA and in Chile     are notable localities.
Name Origin:	From the Latin, cuprum, meaning copper.

Crystallography

Axial Ratios:	a:b:c =1.7321:1:1.6318
Cell Dimensions:	a = 4.2696, Z = 2; V = 77.83 Den(Calc)= 6.11
Crystal System:	Isometric - HexoctahedralH-M Symbol (4/m 3 2/m)     Space Group: P n3m
X Ray Diffraction:	By Intensity(I/Io): 2.465(1), 2.135(0.37), 1.51(0.27)

Image

Cuprite, red crystals. Image Source: R.Weller/Cochise College

SPHALERITE
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides along with calcite, dolomite, and fluorite.

Chemical Composition

Chemical Formula:	(Zn,Fe)S
Composition:	Molecular Weight = 96.98 gm     Zinc 64.06 % Zn     Iron 2.88 % Fe     Sulfur 33.06 % S
Environment:	In sulfide ore veins in all rock classes.
Locality:	Santander-Spain and Joplin-Kansas.     are notable localities.
Name Origin:	From the Greek sphaleros - "misleading."

Crystallography

Axial Ratios:	a:b:c =1.7321:1:1.6318
Cell Dimensions:	a = 5.406, Z = 4; V = 157.99 Den(Calc)= 4.08
Crystal System:	Isometric - HextetrahedralH-M Symbol (4 3m)     Space Group: F43m
X Ray Diffraction:	By Intensity(I/Io): 3.123(1), 1.912(0.51), 1.633(0.3)

Image

Sphalerite crystals from Peru. Image Source: R.Weller/Cochise College

CALCITE
Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar" while the rhombohedral form is sometimes referred to as "nailhead spar". Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. Approximately 10% of sedimentary rock is limestone.

Chemical Composition

Chemical Formula:	CaCO3
Composition:	Molecular Weight = 100.09 gm     Calcium 40.04 % Ca 56.03 % CaO     Carbon 12.00 % C 43.97 % CO2     Oxygen 47.96 % O
Environment:	Found in sedimentary, igneous, and metamorphic rocks.
Locality:	Common world wide.
Name Origin:	From the Latin, calx, meaning lime.

Crystallography

Axial Ratios:	a:c = 1:3.41992
Cell Dimensions:	a = 4.989, c = 17.062, Z = 6; V = 367.78     Den(Calc)= 2.71
Crystal System:	Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m)     Space Group: R 3c
X Ray Diffraction:	By Intensity(I/Io): 3.035(1), 2.095(0.18), 2.285(0.18)

Image

calcite-dogtooth spar crystals-4N Mexico Image Source: R.Weller/Cochise College