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GEOREF RECORD

The occurrence of tinsleyite in the archaeological site of Santana do Riacho, Brazil

Geraldo Magela da Costa and Rubia Ribeiro Viana
The occurrence of tinsleyite in the archaeological site of Santana do Riacho, Brazil
American Mineralogist (September 2001) 86 (9): 1053-1056

Abstract

A second occurrence of tinsleyite, KAl (sub 2) (PO (sub 4) ) (sub 2) (OH).2H (sub 2) O, is reported. The mineral exists as a thin layer in a quartzite wall partially covered by rock paintings, and was characterized by X-ray diffraction, thermal and chemical analysis, and by Mossbauer spectroscopy. The calculated cell parameters are a = 9.58(6), b = 9.53(4), c = 9.54(6) Aa, beta = 103.2(4) degrees . Chemical analysis showed the presence of 3.9% Fe which probably replaces Al in the octahedral site. The Mossbauer spectra from room temperature down to 85 K show the existence of two Fe (super 3+) doublets with Delta E (sub Q1) approximately 0.57 mm/s and Delta E (sub Q2) approximately 1.0 mm/s. At 77 K the spectrum drastically changes, suggesting that a structural transition might have occurred. The formation of tinsleyite might be due to the reaction of phosphate-rich water which runs along the fractures of the wall. The existence of tinsleyite in such a relatively large abundance indicates that this mineral might not be rare as previously thought.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 86
Serial Issue: 9
Title: The occurrence of tinsleyite in the archaeological site of Santana do Riacho, Brazil
Affiliation: Universidade Federal de Ouro Preto, Chemistry Department, Ouro Preto, Brazil
Pages: 1053-1056
Published: 200109
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 11
Accession Number: 2002-012018
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
S23°30'00" - S14°00'00", W51°00'00" - W39°45'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200205
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