Riebeckite

<p>Riebeckite is a <a href="/facts/Sodium/eYuSPu2V">sodium</a>-rich member of the <a href="/facts/Amphibole/2Nf6RDRA">amphibole</a> group of <a href="/facts/Silicate_mineral/WclrQW2I">silicate minerals</a>, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a <a href="/facts/Solid_solution/Mla7z8dc">solid solution</a> series with magnesioriebeckite. It crystallizes in the <a href="/facts/Monoclinic/5PCwXvzX">monoclinic</a> system, usually as long <a href="/facts/Prism_(geometry)/baIRRkCy">prismatic</a> <a href="/facts/Crystal/e2R2mk3E">crystals</a> showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its <a href="/facts/Mohs_hardness/wXBMcVIm">Mohs hardness</a> is 5.0–6.0, and its <a href="/facts/Specific_gravity/ySquGd2x">specific gravity</a> is 3.0–3.4. <a href="/facts/Cleavage_(crystal)/p4YHe01X">Cleavage</a> is perfect, two directions in the shape of a <a href="/facts/Diamond/IBUdnd1y">diamond</a>; fracture is uneven, splintery. It is often translucent to nearly opaque.
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Riebeckite open-in-new

Riebeckite