Feldspar Group

Classification:

Feldspar minerals are the most common group of minerals in the lithosphere. These minerals include orthoclase, microcline, and sanidine (alkalifeldspars), as well as albite, oligoclase, andesin, labradorite, bytownite, and anorthite (plagioclase group).

Synonyms/Trade Names:

Feldspat.

Chemistry/Composition:

The alkalifeldspars (K,Na)(AlSi₃O₈) contain usually <10% of Cafeldspar. The plagiclase group Na(AlSi₃O₈)Ca(Al₂Si₂O₈) usually contains <10% of alkalifeldspar.
This mineral group includes: Orthoclase: K(AlSi₃O₈) (= Or) Sanidine: Or100 0r38Ab63
Anorthoclase: Or37Ab63 Or10Ab90
Albite: Na(AlSi₃O₈) (= Ab) Oligoclase: Ab90An10 Ab70An30
Andesine: Ab70An30 Ab50An50
Labradorite: Ab5An50 Ab30An70
Bytownite: Ab30An70 Ab10An90
Anorthite: Ca(Al₂Si₂O₈) (= An)

Structure:

Potassium-feldspars: Arbitrarily distributed silicon and aluminum atoms are tetrahedrally linked by oxygen atoms, which share the edges of neighboring tetrahedra. The structure can be described by a parallel arrangement of chains, giving the fifth tetrahedron the same position as the first one. In a second description the chains create rings, which are tilted out of horizontal plane. In the large cavities of this network, potassium ions are placed and irregularly linked by nine oxygen atoms. Opposite to the sanidin e structure described, the orthoclas e structure is characterized by partially ordered distribution of Si and Al atoms at the tetrahedral positions. Sodium feldspars: The structure of albite is related to that of sanidine. It has a lower symmetry due to the different sizes of potassium and sodium atoms. The Si and Al atoms are in a tetrahedrally ordered distribution.

Crystallographic Constants:

As described under the particular headings.

Crystal Group:

High-temperature feldspars are monoclinic, and low-temperature feldspars are triclinic.

Color:

As described under the particular headings.

Optical Properties:

As described under the particular headings.

Pleochroism:

As described under the particular headings.

Powder Diagram:

As described under the particular headings.

Natural Sources:

Feldspars are found world-wide.

Medical Importance:

Key Hazards:

Possibly fibrogenic, possibly mutagenic.

Involved Organs:

Possibly lung.

Exposure/Epidemiology:

Feldspars are widely used in the ceramic industry, as building materials. Exposure may occur in mining or usage.

Thresholds:

In Germany, MAK 6 mg/m3.

Etiology/Pathophysiology:

Animal experiments of intraperitoneally feldspars injections in rats revealed a mild fibrogenic potency; however, these findings could not be confirmed in guinea pigs.

Lung Diseases:

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

Dumortier P, De Vuyst P, Yernault JC: Non-fibrous inorganic particles in human Bronchoalveolar Lavage. Scanning Micros 3 (1989) 1207-1218
Gault MH, Campbell NR, Aksu AE: Spurious stones. Nephron 48 (1988) 274-279
Reichel G: Auf anorganische Stäube mit geringem oder fehlendem Quarzgehalt zurückgehende Lungenveränderungen. In: WT Ulmer (Ed): Handbuch der inneren Medizin, Bd IV: Pneumokoniosen. Springer, Heidelberg (1978) 468-508
Stenstrom TA: Bacterial hydrophobicity, an overall parameter for the measurement of adhesion potential to soil particles. Appl Environ Microbiol 55 (1989) 142-147
Wylie AG, Bailey KF: The mineralogy and size of airborne chrysotile and rock fragments: ramifications of using the NIOSH 7400 method. Am Ind Hyg Ass J 53 (1992) 442-447
Zaid SH: Experimental pneumoconiosis. The John Hopkins Press, Baltimore (1969)