Actinolite

Classification:

Actinolite is a Ca₂+and Mg²⁺rich mineral of the amphibole group; for details, see under the heading amphibole.

Cas:

77536-66-4

Synonyms/Trade Names:

Bergleder, Byssolith (Amiantus), Kupferit, Taphilit.

Chemistry/Composition:

Ca₂(Mg,Fe)₅((OH,F)/Si₄O₁₁)₂ . Fe can replace Mg in a percentage 6-13%, rarely >50%. Infrequently, it contains MnO (normally <0.3% of weight) .

Structure:

The silicon and aluminum atoms containing oxygen tetrahedra are linked and form chains. Two of these chains are always bonded, forming 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:

9.850 18.100 5.300 90.000 104.833 90.000.

Crystal Group:

Monoclinic.

Color:

Pale to dark green.

Optical Properties:

nx=1.647 ny=1.659 nz=1.667.

Pleochroism:

Yellow to green.

Powder Diagram:

2.72 2.54 3.40 8.47 (25-157).

Natural Sources:

Austria, China, Great Britain, Poland, the Polynesian Islands, and Switzerland.

Varieties:

• Amiantus

Specification:

Amiantus is a mineral and the fibrous crystallized form of actinolite . It is synonymous with asbestos. For details, see under the heading asbestos .

Chemistry/Composition:

Identical to actinolite .

Structure:

Identical to actinolite .

Crystallographic Constants:

Identical to actinolite .

Crystal Group:

Identical to actinolite .

Color:

Identical to actinolite .

Optical Properties:

Identical to actinolite .

Pleochroism:

Identical to actinolite .

Powder Diagram:

Identical to actinolite .

Natural Sources:

World-wide, especially in Finland, Italy, Russia, and the USA.

• Ferroactinolite

Specification:

Fe²⁺ can replace Mg²⁺ in actinolite . crystals; the compositions between actinolite and ferroactinolite vary broadly. The latter is the name of the minerals containing >50% Fe²⁺ instead of Mg²⁺ .

Chemistry/Composition:

Ca₂Fe₅((OH,F)/Si₄O₁₁)₂ .

Structure:

Identical to actinolite .

Crystallographic Constants:

Not known.

Crystal Group:

Identical to actinolite .

Color:

Identical to actinolite .

Optical Properties:

nx=1.688 ny=1.699 nz=1.704.

Pleochroism:

Yellow to green.

Powder Diagram:

Identical to actinolite .

Natural Sources:

Deposits are scarce, but world-wide.

• Nephrite

Specification:

Nephrite is a mineral and a cryptocrystalline variety of actinolite . It is one of the two varieties of acmite; for details, see under the heading acmite.

Chemistry/Composition:

Identical to actinolite .

Structure:

Identical to actinolite .

Crystallographic Constants:

Identical to actinolite .

Crystal Group:

Identical to actinolite .

Color:

Normally green, seldom grayish-green.

Optical Properties:

Identical to actinolite .

Pleochroism:

Identical to actinolite .

Powder Diagram:

Identical to actinolite .

Natural Sources:

China, Italy, New-Zealand, and Russia (Lake Baikal).

Medical Importance:

Key Hazards:

Fibrogenic, carcinogenic.

Involved Organs:

Lung, peritoneum, skin, gastrointestinal tract, kidneys, lymphatic system.

Exposure/Epidemiology:

Actinolite minerals have specific physical properties, such as heat resistance, high electrical resistance, etc., and are often used in industry. They belong to the asbestos minerals; for details, see under the heading asbestos .

Thresholds:

See under the heading asbestos .

Etiology/Pathophysiology:

Inhaled fibers activate complement-derived chemotactic activity on alveolar surfaces, pneumocytes, macrophages, and mesothelial cells. Chromosome abnormalities, oxygen radicals and immunologic elements such as interleukins and tumor necrosis factor, are probably involved.

Lung Diseases:

The fibrous Varieties are carcinogenic and can induce mesotheliomas (predominantly), or less often other malignancies (carcinoma) of the lower respiratory tract; for details, see under the headings amphibole and asbestos .

Clinical Presentation:

Chronic cough, shortness of breath during physical exercise, pleural effusions, and chest pain with mesothelioma.

Radiology:

Early changes may not be seen on chest radiographs, which normally demonstrate diffuse interstitial infiltrates, pleural effusions, and pleural thickening. Radiological changes are classified under the ILO scheme into three categories according to size and distribution of the morphological changes.

Lung Function:

Restrictive alterations are usually present in early stages. Advanced stages may reveal severe disturbance of lung compliance. Obstructive changes can be demonstrated less frequently.

Bronchoalveolar Lavage:

The mineral fibers may be detected and quantified in the BAL. Increased levels of complement C5a have been described. The ratio of T4/T8 lymphocytes, the levels of angiotensine converting enzyme, and the total number of inflammatory cells are not related to the degree and period of exposure.

Pathology:

Gross:

Early changes may not be detectable. Pleural effusions are usually clear and of yellowish color, and in the case of mesothelioma bloody. Grayish-white pleural plaques measure from a few millimeters to several centimeters. Mesotheliomas are of yellowish -red color and display necrotic areas of various size. The lung parenchyma displays increased consistency. Honeycombing may be seen in advanced stages.

Histology:

The mineral fibers are birefringent, normally deposited in the peripheral airways (bronchioles and alveoli), and less frequently in the intrapulmonary lymphatic tissue. They can be ingested by macrophages. The interstitial fibrosis is of the “diffuse type” and usually not related to larger bronchi or blood vessels. Pleural plaques do not contain mineral fibers. They are formed by acellular hyaline material and collagenous fibers, and contain empty spindle-shaped spaces (basketweave appearance). Weak mononuclear interstitial inflammatory infiltrates and an increased number of intra-alveolar macrophages are common findings.

Classification

of the mineral fibers by light microscopy is not possible.

Prognosis:

Prognosis of patients with long lasting and intensive exposure is poor. Induced interstitial fibrosis is slowly progressive and is not responsive to therapy. Median survival of patients with mesothelioma is less than one year after clinical diagnosis, and independent from the inducing agent.

Additional Diseases:

The minerals belong to the group of asbestiform fibers and can probably induce benign and malignant tumors of various organs; for details, see under the heading asbestos .

References:

search Pubmed for Actinolite

Gaensler EA, Jederlinic PJ, Churg A: Idiopathic pulmonary fibrosis in asbestos-exposed workers. Am Rev Respir Dis 144 (1991) 689-696
Hessel PA, Sluis-Cremer GK: X-ray findings,Lung Function, and respiratory symptoms in black South African vermiculite workers. Am J Ind Med 15 (1989) 21-29
Lewis RJ: Carcinogenically active chemicals. Van Nostrand Reinhold, New York (1991)
Merchant A: Human epidemiology: a review of fiber type and characteristics in the development of malignant and nonmalignant disease. Environ Health Perspect 88 (1990) 287-293
Oehlert GW: A reanalysis of the Stanton et al. pleural sarcoma data. Environ Res 54 (1991) 194-205
Pott F, Roller M, Ziem U, Reiffer FJ, Bellmann B, Pinkenbruch M, Huth F: Carcinogenicity studies on natural and man-made fibers with the intraperitoneal test in rats. IARC Sci Publ 90 (1989) 173-179