Agardite-(La) – Occurrence, Properties, and Distribution

Jun 12 2014

Topics Covered

Introduction to Agardite-(La)
Properties of Agardite-(La)
How to Identify Agardite-(La)
Global Distribution
Occurrence of Agardite-(La) and Useful Mineral Association
References

Introduction to Agardite-(La)

Chemical Formula - (La, Ca) Cu₆ (AsO₄)₃(OH)₆ •3H₂O

Agardite-(La) was named by Peter J. Modreski in 1983 as an analogy to agardite-(Y), with its rare-earth content dominated by lanthanum. This mineral belongs to the mixite group.

Properties of Agardite-(La)

The following are the key properties of agardite-(La):

Cell Data
- Space group: P6₃/m or P6₃
- a = 13.586(4)
- c = 5.931(5)
- Z = 2

Crystal Data
- Hexagonal
- Point group: 6/m or 6
- Acicular, prismatic, to 3mm
- In tufted groups
- Spherical rosettes

Optical Properties
- Semi-transparent
- Optical class: Uniaxial (+)
- ω = 1.715(2)
- ε = 1.795(2)

Estimated Properties

Electron density	Bulk density (electron density) = 3.51 g/cm³ note: Specific gravity of Agardite-(La) = 3.74 g/cm³
Photoelectric	PE_{Agardite-(La)} = 75.43 barns/electron U = PE_{Agardite-(La)} x ρ electron density = 264.47 barns/cm³
Fermion index	Fermion index = 0.00025 Boson index = 0.99974
Radioactivity	Agardite-(La) is radioactive

How to Identify Agardite-(La)

Agardite-(La) can be identified in the field by its color variations, such as yellowish-green, and blue. It can also be colorless. It is transparent, and has a vitreous luster, with greenish-white streak.

The density of agardite-(La) is 3.72 g/cm³, with a hardness of 3 to 4 - between calcite and fluorite.

Global Distribution

Agardite-(La) is distributed in the following places:

USA - From the Red Cloud fluorite and copper mines, Gallinas district, Lincoln Co. New Mexico
Greece - In the Kamariza mine, Laurium
England - From Wheal Alfred, Phillack, Cornwall; at the Brandy Gill and Deer Hills mines, Caldbeck Fells, Cumbria
Italy - From the Sa Duchessa mine, near Iglesias, Sardinia
Germany - In the Clara Mine, near Oberwolfach, and other localities in the Black Forest

Occurrence of Agardite-(La) and Useful Mineral Association

Agardite-(La) occurs in small amounts in the oxidized zone of hydrothermal mineralized breccia and polymetallic mineral deposits.

It is often associated with minerals such as fluorite, bastnaesite, barite, quartz, chrysocolla, azurite, malachite, mimetite, vanadinite, conichalcite, mottramite, cerussite, smithsonite, wulfenite, aurichalcite, hydrozincite, azurite, cuprian adamite, chrysocolla, zincaluminite, gibbsite, and calcite.