Orthoclase

Classification:

Orthoclase belongs to the feldspar group.

Synonyms/Trade Names:

Kalifeldspat.

Chemistry/Composition:

K(AlSi3O8) . It can contain Na, Ba, Fe2+, or Fe3+ .

Structure:

The tetrahedra which contain silicon and aluminum atoms are linked by common oxygen atoms and point into all directions. The structure can be described by rings of four tetrahedra, which are placed in sheets, and form chains. The orthoclas e structure displays a partial order of silicon and aluminum atoms. Potassium atoms are placed in large cavities.

Crystallographic Constants:

8.560 13.000 7.190 90.000 116.000 90.000.

Crystal Group:

Monoclinic.

Color:

Varies from yellowish-brown to reddishwhite.

Optical Properties:

nx=1.518-1.523 ny=1.522-1.530 nz=1.523-1.532.

Pleochroism:

In thin sections, colorless and without Pleochroism.

Powder Diagram:

3.31 3.77 4.22 3.24 (31-966).

Natural Sources:

World-wide.

Varieties:

• Hyalophane

Specification:

Hyalophane is a barium containing feldspar, which can crystallize in an fibrous form.

Chemistry/Composition:

(K,Ba)(Al(Al,Si)Si2O8) . It can contain Na, Ca, or Sr .

Structure:

The tetrahedra which contain silicon and aluminum atoms are linked by common oxygen atoms and point in all directions. The structure can be described by rings of four tetrahedra, which are placed in sheets, and form chains. The orthoclase structure displays a partial order of silicon and aluminum atoms. Potassium atoms are placed in large cavities.

Crystallographic Constants:

8.520 12.950 7.140 90.000 116.000 90.000.

Crystal Group:

Monoclinic.

Color:

Normally colorless, seldom gray.

Optical Properties:

nx=1.518-1.585 ny=1.521-1.589 nz=1.524-1.595.

Pleochroism:

In thin sections, colorless and without Pleochroism.

Powder Diagram:

Data not available.

Natural Sources:

Australia (Broken Hill/NSWales), Japan (Kaso mine), the RSA (Otjosundo), and Switzerland (Binna Valley).

Medical Importance:

Key Hazards:

Possibly fibrogenic, possibly mutagenic.

Involved Organs:

Probably lung.

Exposure/Epidemiology:

Exposure may occur during usage in glass and ceramic industries.

Thresholds:

In Germany, MAK 6 mg/m3.

Etiology/Pathophysiology:

Detailed data are not known.

Lung Diseases:

Associated specific diseases are not known; however, the mineral is listed by the ISO, i.e., fibrogenic and possibly mutagenic forms exist.

Clinical Presentation:

Associated specific symptoms are not known.

Radiology:

Associated specific findings are not known.

Lung Function:

Usually normal findings.

Bronchoalveolar Lavage:

Usually normal findings.

Pathology:

Gross:

The lungs are of normal color and consistency.

Histology:

The alveoli can contain an increased number of macrophages, and collections of brown dust particles may be seen in the lymphatic tissue.

Prognosis:

Usually good and without serious sequelae.

Additional Diseases:

None.

References:

search Pubmed for Orthoclase