engleski

Morphology investigation of brazilianite from different localities

On the morphology of brazilianite there hasn’t been published many papers since it’s discovery [1]. From the importance of crystallogenetic study and possible differences between material from different localities arises need for a study of brazilianite crystals. Two circle goniometric measurements were performed on 34 single crystals of brazilianite from different localities in Brazil. 26 measured crystals originate from Telírio claim, Linopolis, Divino das Laranjeiras, one from Divino das Laranjerias province (exact mine not determined), three from São Geraldo do Baixio district and four from Araçuai region. All brazilianite crystals are well developed, but were probably attached to matrix on one end of [100] so in almost all crystals that side is missing. Crystals colour ranges from yellow, through yellowish-greenish to green, while some crystals are colourless. All forms in [001] zone are striated parallel to [001]. Forms that occur on every measured brazilianite crystal are {; ; ; 010}; ; ; and {; ; ; 110}; ; ; and they are striated. Other forms that are very common are: {; ; ; 011}; ; ; , {; ; ; -111}; ; ; , {; ; ; 211}; ; ; and {; ; ; -101}; ; ; . Four forms, not measured before, appear on investigated crystals. These are: {; ; ; 143}; ; ; , {; ; ; 520}; ; ; , {; ; ; 322}; ; ; and a form with {; ; ; hkl}; ; ; indices. Indices for the {; ; ; hkl}; ; ; form could not be exactly determined due to restrictions in precision of stereographic/gnomic projection. The face is very gently inclined and close to {; ; ; 001}; ; ; . There is a record of several habits of brazilianite crystals in literature [1, 2]. Several new habits can be distinguished after these measurements (fig. 1). Two new habits, together with four new forms are recognized during this morphological investigation of brazilianite crystals.

brazilianite; morphology; different localities

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