Barroisite

Classification:

Barroisite belongs to the hornblende group and is related to tschermakite, and is scarce; compare to hornblende and tschermakite.

Synonyms/Trade Names:

Amphibole, hornblende, tschermakite.

Chemistry/Composition:

Ca2(Mg,Fe2+)3(Al,Fe3+)2((OH)2/Al2Si6O22) .

Structure:

The silicon and aluminum atoms containing oxygen tetrahedra are linked and form chains. Two of these chains are bonded, respectively, and form a double chain, which is built by rings of six-membered tetrahedra. Two tetrahedra belong to the two neighboring rings, respectively, and only two of them to the ring itself. The chains can be described by the chemical formula (Si4O11)n. The separated chains are bonded by cations and partially by hydroxyl ions.

Crystallographic Constants:

9.900 18.000 5.300 90.000 105.000 90.000.

Crystal Group:

Monoclinic.

Color:

Green.

Optical Properties:

nx=1.640-1.673 ny=1.649-1.690 nz=1.658-1.696.

Pleochroism:

colorless to yellow.

Powder Diagram:

3.11 2.75 2.35 2.18.

Natural Sources:

World-wide.

Medical Importance:

Key Hazards:

Possibly fibrogenic, possibly mutagenic.

Involved Organs:

None.

Exposure/Epidemiology:

Exposure or technical use are not known.

Thresholds:

In Germany, MAK 6 mg/m3.

Etiology/Pathophysiology:

Associated risks are not known.

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:

No associated symptoms are known.

Radiology:

Chest radiographs are usually normal.

Lung Function:

Usually normal.

Bronchoalveolar Lavage:

The mineral fibers can be detected in the lavage fluid.

Pathology:

Gross:

The lungs display no abnormal findings.

Histology:

The mineral fibers can be deposited in the distant airways, ingested by macrophages, and transferred to the proximal lymph nodes. An increased number of intra-alveolar macrophages and mild mononuclear inflammatory infiltrates may be noted.

Prognosis:

Usually good and without serious sequelae.

Additional Diseases:

None.

References:

search Pubmed for Barroisite