Hornblende

Classification:

It is defined as a group of minerals, which belong to the amphiboles; compare to amphibole .

Synonyms/Trade Names:

Amphiboles.

Chemistry/Composition:

Ca₂(Na,K)0,5-1(Mg,Fe²⁺)3Fe³⁺,Al)₂-1((O,OH,F)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:

9.880 18.020 5.330 90.000 105.500 90.000.

Crystal Group:

Monoclinic.

Color:

Related to the specific mineral composition and described under the specific heading.

Optical Properties:

Related to the specific mineral composition and described under the specific heading.

Pleochroism:

Related to the specific mineral composition and described under the specific heading.

Powder Diagram:

Related to the specific mineral composition and described under the specific heading.

Natural Sources:

World-wide.

Varieties:

• Barroisite

Specification:

Barroisite is a rare member of the hornblende group.Chemistry: Ca₂(Mg,Fe²⁺)3(Fe³⁺,Al)₂((O,OH,F)₂/Al₂Si₆O₂₂) .

Structure:

Identical to hornblende.

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.

• Edenite

Specification:

Edenite is a seldom found member of the hornblende group.

Chemistry/Composition:

NaCa₂Mg5((OH,F)₂/AlSi₇O₂₂) .

Structure:

Identical to hornblende.

Crystallographic Constants:

9.900 18.000 5.300 90.000 105.000 90.000.

Crystal Group:

Monoclinic.

Color:

colorless or green.

Optical Properties:

nx=1.6 ny=1,6 (nx = ny) nz=1.7.

Pleochroism:

Variable, varies from blue to green.

Powder Diagram:

3.12 8.43 3.27 2.70 (23-1405).

Natural Sources:

Finland (Pargas), Sri Lanka, and the USA (Edenville/New York).

• Hastingsite

Specification:

Hastingsite is an often found member of the hornblende group.

Chemistry/Composition:

NaCa₂(Mg,Fe)(Al,Fe³⁺)((OH)₂/Al₂Si₆O₂₂) .

Structure:

Identical to hornblende.

Crystallographic Constants:

9.912 18.030 5.296 90.000 103.946 90.000.

Crystal Group:

Monoclinic.

Color:

Green or black.

Optical Properties:

nx=1.646-1.700 ny=1.658-1.719 nz=1.662-1.722.

Pleochroism:

Changes from green to yellow, and to brown.

Powder Diagram:

8.52 3.16 2.59 2.20 (20-578)
8.43 3.13 2.71 3.39 (20-469).

Natural Sources:

Canada (Hasting/Ontario).

• Kaersutite

Specification:

It is a member of hornblende group.

Chemistry/Composition:

Ca₂(Na,K)( Mg,Fe²⁺,Fe³⁺)4(Ti(( O,OH,F)₂/ Al₂Si₆O₂₂) .

Structure:

Identical to hornblende.

Crystallographic Constants:

9.900 18.210 5.400 90.000 106.000 90.000 (Ferich),9.900 17.210 5.400 90.000 106.000 90.000 (Mg-rich).

Crystal Group:

Monoclinic.

Color:

Dark brown to black or yellow.

Optical Properties:

nx=1.667-1.690 ny=1.680-1.708 nz=1.691-1.717.

Pleochroism:

Yellowish brown to reddish brown.

Powder Diagram:

2.69 3.11 8.38 3.36 (17-478).

Natural Sources:

World-wide.

• Katophorite

Specification:

It is a member of hornblende group.

Chemistry/Composition:

Na₂CaFe²⁺4(Fe³⁺,Al)((OH,F)₂/AlSi₇O₂₂) .

Structure:

Identical to hornblende.

Crystallographic Constants:

9.900 18.000 5.300 90.000 104.000 90.000.

Crystal Group:

Monoclinic.

Color:

Yellow, yellow-red, brown, or bluish.

Optical Properties:

nx=1.640-1.681 ny=1.658-1.688 nz=1.660-1.690.

Pleochroism:

Red to dark brown to opaque.

Powder Diagram:

Data not available.

Natural Sources:

Germany (Odenwald), and Norway (Langesundfjord).

• Pargasite

Specification:

It is a member of hornblende group.

Chemistry/Composition:

NaCa₂Mg5(Al,Fe³⁺)((OH,F)₂/Al₂Si₆O₂₂) .

Structure:

Identical to hornblende.

Crystallographic Constants:

9.900 18.000 5.300 90.000 105.500 90.000.

Crystal Group:

Monoclinic.

Color:

Brown colored, colorless, or seldom bluish.

Optical Properties:

nx=1.611-1.660 ny=1.615-1.673 nz=1.630-1.681.

Pleochroism:

Greenish to bluish.

Powder Diagram:

3.12 8.43 3.27 2.93 (23-1406).

Natural Sources:

Finland (Pargas).

• Tschermakite

Specification:

It is a member of hornblende group.

Chemistry/Composition:

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

Structure:

Identical to hornblende.

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:

Greenish gray to brownish green.

Powder Diagram:

3.11 2.75 2.35 2.18.

Natural Sources:

World-wide.

Medical Importance:

Key Hazards:

Fibrogenic, carcinogenic.

Involved Organs:

Lung, peritoneum, skin, kidneys.

Exposure/Epidemiology:

The hornblende minerals belong to the amphibole minerals and 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 compartments such as interleukins and tumor necrosis factor are probably involved. For details, see under the heading asbestos .

Lung Diseases:

All amphibole minerals 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:

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