Forsterite Mg2SiO4
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mineral forsterite
It is the magnesium-rich end component of the olivine solid solution series. It is isomorphic to iron-rich terminal fayalite crystallized in orthorhombic form.
We have always believed that forsterite is associated with igneous and metamorphic rocks. We found it in meteorites too. In 2005, it was also found in cometary dust returned by the Stardust probe. In 2011, it was observed as tiny crystals in dusty gas clouds around an emerging star.
There are two polymorphs of this stone. Wadsleyite, rhombic, like ringwoodite, isometric. Both come mainly from meteorites.
A pure crystal is magnesium, as well as oxygen and silicon. Chemical formula Mg2SiO4. Forsterite, fayalite Fe2SiO4 and tephroite Mn2SiO4 are the last members of the olivine solution series. Other elements such as Ni and Ca replace Fe and Mg in olivines. But only in small proportions in natural phenomena.
Other minerals such as monticellite CaMgSiO4. An unusual mineral rich in calcium has the structure of olivine. But there is a small amount of solid solution between olivine and these other minerals. We can find monticellite in contact with transformed dolomites.
Forsterite Composition: Mg2SiO4
The chemical composition is mainly anion SiO44- and cation Mg2+ in a molar ratio of 1:2. Silicon is the central atom of the SiO44- anion. A single covalent bond links each oxygen atom to silicon. Four oxygen atoms are partially negatively charged.
Due to the covalent bond with silicon. Therefore, the oxygen atoms must be far apart. To reduce the force of repulsion between them. The best geometry to reduce repulsion is the tetrahedral shape.
This was first described in 1824 for a case on a mountain. Somma, Vesuvius, Italy. Its name comes from the English naturalist and mineral collector Adolarius Jacob Forster.
The stone is currently being investigated as a potential biomaterial for implants. Due to excellent mechanical properties.
Gemological properties
- Category: mesosilicates
- Formula: magnesium silicate (Mg2SiO4)
- Diamond crystal system
- Crystal class: dipyramidal
- Color: colorless, green, yellow, yellow-green, white;
- Shape of crystals: dipyramidal prisms, often tabular, usually granular or compact, massive.
- Double collaboration: {100}, {011} and {012}
- Neckline: perfect for {010} imperfect for {100}
- Fracture: conchoidal
- Mohs hardness: 7
- Luster: vitreous
- Stripe: white
- Transparency: transparent to translucent
- Specific gravity: 3.21 - 3.33
- Optical properties: biaxial (+)
- Refractive index: nα = 1.636 – 1.730 nβ = 1.650 – 1.739 nγ = 1.669 – 1.772
- Birefringence: δ = 0.033–0.042
- Angle 2B: 82°
- Melting point: 1890°C
forsterite meaning and medicinal properties, metaphysical benefits
The following section is pseudo-scientific and based on cultural beliefs.
The crystal has meaning and healing properties of past wounds. It is a gemstone with strong healing energy. This will put an end to the pain that lingers from the past. It also gives you the strength to look to the future.
FAQ
What are the applications for forsterite?
As gemstones for industrial use as refractory sands and abrasives, magnesium ore and as mineral specimens. The crystal is named after the German naturalist Johann Forster. It is one of two minerals simply referred to as olivine. The second mineral is fayalite.
What is the difference from fayalite?
Fayalite is an iron-rich rock with the pure formula Fe2SiO4. Forsterite is a magnesium-rich ingredient with a pure formula of Mg2SiO4. Otherwise, they are difficult to distinguish, and virtually all samples of these two minerals contain both iron and magnesium.
Where is forsterite mined?
The stone is commonly found in dunites, gabbras, diabases, basalts and trachytes. Small amounts of fayalite are present in many volcanic rocks where sodium is more common than potassium. These minerals are also found in dolomitic limestones, marbles, and iron-rich metamorphoses.
How to calculate the olivine content in forsterite?
Plot of olivine-forsterite content (Fo = 100 * Mg / (total Mg + Fe), proportions of cations) versus the amount of Ca cations (mineral formula based on four oxygen atoms).
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