Asisite – Occurrence, Properties, and Distribution

Sep 26 2013

Topics Covered

Introduction to Asisite
Properties of Asisite
How to Identify Asisite
Global Distribution
Occurrence of Asisite and Useful Mineral Association
References

Introduction to Asisite

Chemical Formula - Pb₇SiO₈Cl₂

Asisite was named after the Asis farm located at the Kombat mine, Namibia.

Properties of Asisite

The following are the key properties of asisite:

Cell Data
- Space group: I 4/ mmm
- a = 3.897(2)
- c = 22.81(2)
- Z = 1
Crystal Data
- Tetragonal
- Point group: 4/m 2/m 2/m
- Platy, to about 0.5 mm
- X-ray powder pattern: 2.957 (100), 2.752 (60), 1.627 (60), 1.602 (50), 3.46 (40), 1.984 (40), 1.747 (40)

Chemical Composition

Elements	Content 1
PbO	93.7
Cl	4.4
SiO₂	2.0
-O = Cl₂	1.0
Total	99.1

Optical Properties
- Optical class: Uniaxial (-)
- ω = 2.39
- ε = 2.32
- Anisotropism: Weak in oil, gray; not noticeable in air
- R1-R2: (400) 20.6-20.7, (420) 19.8-19.8, (440) 19.0-19.15, (460) 18.5-18.65, (480) 18.1-18.2, (500) 17.7-17.9, (520) 17.4-17.55, (540) 17.15-17.3, (560) 16.9-17.0, (580) 16.7-16.8, (600) 16.6-16.7, (620) 16.5-16.5, (640) 16.3-16.4, (660) 16.2-16.3, (680) 16.1-16.2, (700) 16.0-16.1

Estimated Properties

Electron density	Bulk density (electron density) = 6.47 g/cm³ note: Specific gravity of asisite = 7.94 g/cm³
Photoelectric	PE_Asisite = 1,653.44 barns/electron U=PE_Asisite x ρ electron density= 10701.44 barns/cm³
Fermion index	Fermion index = 0.19 Boson index = 0.81
Radioactivity	Asisite is not radioactive

How to Identify Asisite

Asisite can be identified in the field by its green-yellow and yellow color variations. Its transparent form has {001} perfect cleavage.

This mineral has an adamantine luster with yellow white streak. The hardness of asisite is 3.5- approximate to a copper penny.

Global Distribution

Asisite is distributed mainly in Namibia in the Kombat mine, 49 km south of Tsumeb.

Occurrence of Asisite and Useful Mineral Association

Asisite occurs in manganese silicate lenses nearby a sulfide ore body. It is often associated with minerals such hematophanite, chlorite, barite, hematite, molybdophyllite, jacobsite, and copper,