Editorial Feature

Callaghanite - Occurrence, Properties, and Distribution

Jun 4 2014

Callaghanite is a monoclinic-prismatic mineral, consisting of oxygen, magnesium, hydrogen, copper, and carbon.

It was named after Honors Dr. Eugene Callaghan, Director of the New Mexico Bureau of Mines in Socorro, New Mexico, USA, for his work on magnesite deposits.

Properties of Callaghanite

The following are the key properties of Callaghanite:

Cell Data
- Space Group: C2/c
- a = 10.0060(7)
- b = 11.7520(8)
- c = 8.2132(7)
- β = 107°23?

Crystal Data
- Monoclinic
- Point Group: 2/m
- Crystals are pseudo-octahedral to dipyramidal, dominated by {111} and {111}, modified by {122} and {122}, to 3mm
- As incrustations and massive in veinlets
- X-ray powder pattern: 7.45 (10), 6.17 (10), 3.87 (9), 3.18 (9), 2.30 (7), 4.80 (6), 3.72 (6)

Chemical Composition

Elements	Content 1	Content 2
CO₂	11.46	11.77
CuO	38.27	42.56
MgO	20.86	21.57
CaO	8.89	-
H₂O	20.51	24.10
Total	99.99	100.00

Optical Properties
- Optical Class: Biaxial (–)
- Pleochroism: In shades of blue
- Orientation: Z ^ a = 18°
- Dispersion: r > v, strong
- Absorption: Z > Y > X
- α = 1.559
- β = 1.653
- γ= 1.680
- 2V(meas.) = 55°

Estimated Properties

Electron density	Bulk density (electron density) = 2.70 g/cm³ note: Specific gravity of Callaghanite = 2.71 g/cm³
Photoelectric	PE_Callaghanite = 14.80 barns/electron U = PE_Callaghanite x ρElectron density = 39.92 barns/cm³
Fermion index	Fermion index = 0.01 Boson index = 0.99
Radioactivity	Callaghanite is not radioactive

How to Identify Callaghanite

Callaghanite occurs in azure or violet-blue forms. It has a transparent appearance, a vitreous luster, a white streak, and perfect cleavages. The fractures appear brittle, producing uneven fragments.

It has an average density of 2.71 g/cm³, and its relative hardness is in the range of 3 to 3.5.