J 2015

Optical and crystal-chemical changes in aquamarines and yellow beryls from Thanh Hoa province, Vietnam induced by heat treatment

FRIDRICHOVÁ, Jana, Peter BAČÍK, Petra RUSINOVÁ, Peter ANTAL, Radek ŠKODA et. al.

Basic information

Original name

Optical and crystal-chemical changes in aquamarines and yellow beryls from Thanh Hoa province, Vietnam induced by heat treatment

Authors

FRIDRICHOVÁ, Jana (703 Slovakia), Peter BAČÍK (703 Slovakia), Petra RUSINOVÁ (703 Slovakia), Peter ANTAL (703 Slovakia), Radek ŠKODA (203 Czech Republic, guarantor, belonging to the institution), Valeria BIZOVSKA (703 Slovakia) and Marcel MIGLIERINI (703 Slovakia)

Edition

Physics and Chemistry of Minerals, NEW YORK, SPRINGER, 2015, 0342-1791

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10500 1.5. Earth and related environmental sciences

Country of publisher

United States of America

Confidentiality degree

není předmětem státního či obchodního tajemství

Impact factor

Impact factor: 1.585

RIV identification code

RIV/00216224:14310/15:00087129

Organization unit

Faculty of Science

DOI

UT WoS

000351463100004

Keywords in English

Beryl; Heat treatment; Powder X-ray diffraction; Infrared spectroscopy; Mossbauer spectroscopy; Electron microprobe; UV/Vis/NIR spectroscopy; Raman spectroscopy

Tags

Změněno: 7/4/2016 15:27, Ing. Andrea Mikešková

Abstract

V originále

Optical and crystal-chemical changes in two beryl varieties after the heat treatment were determined using a wide spectrum of analytical methods. Studied aquamarines are generally more enriched in Fe (up to 0.25 apfu) and alkali (up to 0.08 apfu) than yellow beryls (up to 0.07 apfu Fe, up to 0.04 apfu alkali). The determined c/a ratio of 0.997-0.998 classified all our studied beryls as "normal" beryls. While no crystal structure changes were observed in samples heated to 700 A degrees C, those heated to 900 and 1,100 A degrees C exhibited cracks and fissures. Reduced Fe occurred in samples heated between 300 and 700 A degrees C, and subsequent oxidation from 900 to 1,100 A degrees C induced changes in their colour and clarity. The Fe-bearing beryl colour is controlled by the position of the absorption edge and the presence of a broad band attributed to Fe2+ in the NIR region. Blue colour results from the absorption edge located deeper in the UV region and the presence of broad band in the NIR region. Shift of absorption edge to the visible region at the presence of the broad band gives a yellow colour. Although our studied beryls are enriched in H2O I molecule due to their low alkali content, the H2O II molecule is also present. The following two dehydration processes were observed: (1) release of one double-coordinating H2O II molecule at 300-500 A degrees C and (2) total dehydration at 900-1,100 A degrees C. The observed cracks and fissures likely resulted from channel water release in large beryl crystals.