Gedrite
Classification:
Gedrite is related to anthophyllite, which is described by the formula (Mg,Fe)7(OH/Si4O11)2 . The two minerals differ in the content of Mg and Fe, which is higher in anthophyllite compared to gedrite. Both minerals can crystallize in a fibrous form, and are then called asbestos ; compare to antigorite, asbestos .
Synonyms/Trade Names:
Asbestos.
Chemistry/Composition:
(Mg,Fe)6-5Al1-2(OH/(Al,Si)Si3O11)2 .
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:
18.594 17.890 5.304 90.000 90.000 90.000.
Crystal Group:
Orthorhombic.
Color:
Gray, yellow or brown.
Optical Properties:
n x = 1.67 4(-1.642) ny=1.681(-1.651) nz=1.691(-1.658).
Pleochroism:
Yellow to brown.
Powder Diagram:
6.70 3.72 3.68 2.80 (35-611).
Natural Sources:
Finland, France, Germany (Black Forest), Greenland, and Norway.
Medical Importance:
Key Hazards:
Fibrogenic, carcinogenic.
Involved Organs:
Lung, peritoneum, skin, kidneys.
Exposure/Epidemiology:
The serpentine minerals are of great technical interest. Their fibrous form is related to their specific physical properties such as heat resistance, electrical insulation, etc. Important sources of exposure are shipyards, manufacture of fire-resistant textiles, sheets, automobile brakes, filters for various fluids, etc. For details, see under the heading asbestos .
Thresholds:
See under the heading asbestos .
Etiology/Pathophysiology:
The inhaled fibers activate complement-derived chemotactic activity on alveolar surfaces, pneumocytes, macrophages, and mesothelial cells. Immunologic components such as interleukins and tumor necrosis factor are probably involved. For details, see under the heading asbestos .
Lung Diseases:
All serpentines can crystallize in fibrous varieties, and can induce interstitial lung fibrosis, pleural diseases such as fibrosis, pleural plaques, benign and malignant tumors of the lung, pleura, peritoneum, gastrointestinal tract, lymphatic system, and kidneys. For details, see under the heading asbestos .
Clinical Presentation:
Chronic cough and shortness of breath during physical exercise are usually the first symptoms; chest pain is often associated with pleural tumors.
Radiology:
Chest radiographs are often normal in patients with early changes. Others may display diffuse interstitial densities, pleural thickening or effusion.
Lung Function:
Progressive restrictive changes or severe obstructive alterations are seen.
Bronchoalveolar Lavage:
The inhaled mineral fibers can be analyzed and quantified in the lavage fluid. Increased levels of complement C5 or altered ratio of the T4/T8 lymphocytes correspond with the activity of the fibrotic lesions.
Pathology:
Gross:
The lungs may display an increased consistency, a thickened and fibrotic pleura, honeycombing, or circumscribed white-yellowish tumor masses. For details, see under the heading asbestos .
Histology:
The fibers are birefringent and often coated with iron-protein mucopolysaccharide substances (asbestos bodies). They are usually deposited in the distant air ways and can be ingested by macrophages. Diffuse interstitial fibrosis associated with scattered mononuclear inflammatory infiltrates and acellular collagenous fibers in the pleura are common findings. Benign and malignant tumors of various cell types (most frequently common lung carcinoma and mesothelioma) can develop. For details, see under the heading asbestos .
Prognosis:
Usually poor due to serious sequelae.
Additional Diseases:
See under the heading asbestos .
References:
search Pubmed for Gedrite
Kayser K: Analytical lung Pathology. Springer, Heidelberg, New York (1992)