Editorial Feature

Fairchildite – Occurrence, Properties, and Distribution

May 7 2013

Fairchildite was named after John Gifford Fairchild, an analytical chemist working with the U.S. Geological Survey. This mineral was discovered in 1946, and it is a dimorph of Bütschliite.

Properties of Fairchildite

The following are the key properties of Fairchildite:

Cell Data
- Space group: P63/mmc
- a = 5.294(1)
- c = 13.355(2)
- Z = 2
Crystal Data
- Hexagonal
- Point group: 6/m 2/m 2/m
- As microscopic hexagonal plates, flattened on {0001}
- Basically in dense stony aggregates
- X-ray powder pattern: Synthetic.
- 3.192 (100), 2.646 (70), 2.699 (30), 2.168 (20), 2.225 (16), 6.67 (14), 2.039 (14)
Chemical Composition
There is no available chemical data of a pure natural material; however this mineral’s identification is based on the coincidence of other properties with those of synthetic material.
Optical Properties
- Optical class: Uniaxial (–)
- ω = 1.533
- ε = 1.498

Estimated Properties

Electron density	Bulk density (electron density) =2.46 gm/cm³ note: Specific gravity of fairchildite =2.48 gm/cm³.
Photoelectric	PE_Fairchildite = 5.47 barns/electron U=PE_Fairchildite x ρelectron= 13.44 barns/cm³
Fermion index	Fermion index = 0.0015686955 Boson index = 0.9984313045
Radioactivity	GRapi = 468.92 (Gamma Ray American Petroleum Institute Units) Concentration of fairchildite per GRapi unit = 0.21(%) Estimated radioactivity from fairchildite- barely detectable

How to Identify Fairchildite

Fairchildite can be identified in the field by its transparent colorless appearance. This mineral has cleavages and occurs as platy sheet forms. It has a glassy lustre with white streak. The density of fairchildite is 2.446 gm/cm³ with a hardness of 2.5 -and so can be scratched by a finger nail.

Global Distribution

Fairchildite is widely distributed in USA but other global locations have also been identified. Some of these are listed below:

USA –The Grand Canyon National Park, Coconino Co., Arizona, and in the Kaniksu National Forest, near Coolin, Bonner Co., Idaho.
Canada - Near Deseronto and Eganville, Ontario
Germany- Rosenberg Mine, Rhineland-Palatinate

Occurrence of Fairchildite and Useful Mineral Association

Fairchildite occurs in fused wood ash in partially burned softwood trees such as fir and hemlock. It is often associated with minerals such as Bütschliite and calcite.