JACOBSITE
JACOBSITE Jacobsite – Mn2+Fe3+2O4 – is a fairly rare oxide, of no importance as an ore. It is classified in the Spinel Supergroup, Magnetite Series. It is magnetic like magnetite, forms a series with magnetite, and is dimorphic with a polymorph of it, jacobsite-Q (Mn2+(Fe3+,Mn3+)2O4), and also with iwakiite. It may exhibit epitaxies with hausmannite […]
JADEITE
JADEITE Jadeite – Na(Al,Fe)Si2O6 – is an inosilicate of the Pyroxene Group, of the Clinopyroxene Subgroup. It is a rather rare mineral, typical of high-grade metamorphic terrains. In South America, for example, it practically does not occur, with the exception of two occasional, non-commercial occurrences in Brazil. It has a very high value as an […]
JADE
JADE Jade is a very rare ornamental stone. The term “jade” is applied to two metamorphic rocks composed of silicates and showing off-white to green colors. Rocks can be formed by: a) Nephrite, which is composed of a matrix formed by fibrous capillary crystals tangles of an amphibole of the Tremolite (Ca-Mg)–Ferroactinolite Series (Ca-Mg-Fe). The […]
JASPER
JASPER Jasper is a rarer variety of chalcedony, therefore one of the silica polymorphs. It is very similar to chalcedony (agate), but chalcedony is fibrous and jasper is granular. It has good acceptance in the ornamental and collection stone market. Geologically the term has been used in relation to impure chalcedony or microcrystalline chert, which […]