RHODONITE
RHODONITE Rhodonite – (Mn,Fe,Mg,Ca)SiO3 – is an inosilicate of the Pyroxene Group. It is a rarer mineral, characteristic of specific paragenesis of Mn minerals. It has no economic importance other than its use as a decorative stone. It is classified in the Rhodonite Group and generally contains traces of Mg, Fe, Al, Zn and Ca. […]
RIEBECKITE
RIEBECKITE Riebeckite – Na2Fe2+3 (Al,Fe3+)2Si8O22(OH)2 – is an inosilicate of the Amphibole Supergroup. It is a comparatively rare mineral. When fibrous, is one of six minerals marketed as “asbestos”, a material that is used less and less nowadays due to the health problems it causes. The variety of riebeckite known as “crocidolite” is the “blue […]
RUTILE
RUTILE Rutile – TiO2 – is a common oxide, an accessory mineral in many igneous rocks. It constitutes an important ore of titanium oxide, which is a high quality white pigment, among other uses. Rutile is one of the 5 polymorphs of TiO2, the others are anatase (tetragonal), brookite (orthorhombic), akaogiite and TiO2 II. Thermodynamically […]
RHÖNITE
RHÖNITE Rhönite – Ca4[Mg8Fe3+2Ti2]O4[Si6Al6O36] – is a fairly rare inosilicate, characteristic of alkaline rocks. It is not an ore. It is classified in the Sapphirine Supergroup, Rhönite Group, along with aenigmatite. It can form prismatic to tabular crystals several centimeters long. It also occurs in skeletal grains with well-developed crystal faces and as anhedral grains. […]
REALGAR
REALGAR Realgar – As4S4 – is a rarer sulfide. It has some importance as an As ore, along with arsenopyrite and orpiment. It normally occurs very pure. It is trimorph with alacránite and pararealgar. Sometimes it’s fluorescent. Macroscopically it can be confused with sarawaite and other red As-S minerals. As realgar is photosensitive, it changes […]
RANCIÉITE
RANCIÉITE Ranciéite – (Ca,Mn2+)0.2(Mn4+,Mn3+)O2·0.6H2O – is a rarer oxide, a minor component of Mn ores, with 75.34% MnO2. It is classified in the Birnessite Group, in the Ranciéite-Takanelite Series, the two being isostructural. Macroscopically it can be confused with todorokite, but X-ray diffractograms are diagnostic, somewhat variable depending on the degree of hydration. The literature […]
RHODOCHROSITE
RHODOCHROSITE Rhodochrosite – MnCO3 – is a rarer carbonate. It is a very secondary ore of Mn and has many uses as a decorative stone, fetching high prices in the collector and ornamental stone market, but it is not suitable for stoning. Once exposed to the atmosphere, it can develop a thin black surface film […]