Magnesio-Ferri-Fluoro-Orneblende 3.86 cts

Cut: Trillion
Dimensions: 10.20 x 10.20 x 7.09mm
Hardness 5-6
SKU: max9958

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Magnesio-Ferri-Fluoro-Orneblende is a complex mineral belonging to the amphibole group, which is a large and diverse group of silicate minerals. The mineral is part of the broader subgroup known as calcic amphiboles, which are typically characterized by their double-chain silicate structure and their composition of calcium, magnesium, and iron among other elements.

Composition and Structure:

The chemical formula of Magnesio-Ferri-Fluoro-Orneblende is generally represented as: (Ca2)(Mg4Fe3+)Si7AlO22F2(Ca_2)(Mg_4Fe^{3+}) \text{Si}_7\text{AlO}_{22}F_2(Ca2​)(Mg4​Fe3+)Si7​AlO22​F2​

This formula reflects the presence of magnesium (Mg), iron in the +3 oxidation state (Fe³⁺), calcium (Ca), silicon (Si), aluminum (Al), oxygen (O), and fluorine (F). The substitution of different cations in the crystal structure, such as the replacement of hydroxide (OH⁻) groups by fluorine (F⁻), gives rise to this specific mineral variant.

Physical Properties

- Crystal System: Monoclinic
- Color: Typically dark green, brown, or black, depending on the exact composition.
- Luster: Vitreous (glassy) to dull.
- Hardness: Ranges from 5 to 6 on the Mohs scale, indicating moderate hardness.
- Cleavage: Exhibits two good cleavages at approximately 56 and 124 degrees, characteristic of amphiboles.

Formation and Occurrence:

Magnesio-Ferri-Fluoro-Orneblende typically forms in metamorphic rocks, particularly those that have undergone high-grade metamorphism, such as schists and gneisses. It can also be found in igneous rocks, particularly those that are silica-undersaturated like certain types of granites and syenites.

Significance:

This mineral is primarily of interest to geologists studying metamorphic processes and the conditions under which certain rocks form. The presence of fluorine in its composition can indicate specific conditions of temperature and pressure during rock formation. It is also relevant in petrology for understanding the chemical environment during the crystallization of the host rocks.

Distinguishing Features:

Magnesio-Ferri-Fluoro-Orneblende can be distinguished from other amphiboles by its specific chemical composition, particularly the dominance of magnesium and iron (ferric iron) along with the fluorine content. The color, hardness, and cleavage patterns are also useful in identifying this mineral in the field or laboratory.