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Hyalotekite from reedmergnerite-bearing peralkaline pegmatite, Dara-i-Pioz, Tajikistan and from Mn skarn, Langban, Varmland, Sweden; a new look at an old mineral

Edward S. Grew, Martin G. Yates, Dimitriy I. Belakovskiy, Roland C. Rouse, Shu-Chun Su and Nicholas Marquez
Hyalotekite from reedmergnerite-bearing peralkaline pegmatite, Dara-i-Pioz, Tajikistan and from Mn skarn, Langban, Varmland, Sweden; a new look at an old mineral
Mineralogical Magazine (June 1994) 58 (2): 285-297

Abstract

In specimens of Mn skarn from the type locality of Laangban, hyalotekite, (Ba,Pb,K) (sub 4) Ca (sub 2-) (Si,B,Be) (sub 12) O (sub 28) F, occurs in a matrix consisting mostly of aegirine (< or =22 mol.% CaMnSi (sub 2) O (sub 6) ), andradite (< or =27 mol.% Mn (sub 3) Fe (sub 2) Si (sub 3) O (sub 12) ), hematite, pectolite, quartz, calcite, baryte, barylite, and hedyphane. Melanotekite, plumbian taramellite, ferrian K-feldspar (to 6.5 wt.% Fe (sub 2) O (sub 3) ), rhodonite, a talc-like mineral, apophyllite, and several Pb-As-Sb-O minerals are found in trace amounts. In a single specimen of reedmergnerite-microcline pegmatite from Dara-i-Pioz, hyalotekite occurs in close association with microcline. Other accessory minerals are albite, aegirine, pyrochlore, eudialyte, and polylithionite. The optical constants for hyalotekite from Laangban and Dara-i-Pioz are, respectively, alpha = 1.656, 1.646, beta = 1.659-1.660, 1.649, gamma = 1.670-1.671, 1.659 (all + or - 0.002), 2Vgamma (mcas) = 57.2-60.5 + or - 0.5 degrees , 57.0 + or - 1.1 degrees (lambda = 589 nm). Cell parameters of the Dara-i-Pioz hyalotekite for a body-centred triclinic cell are: a = 11.284(2), b = 10.930(I), c = 10.272(8) Aa, alpha = 90.35(2) degrees , beta = 90.11(3) degrees , gamma = 89.98(1) degrees . Electron and ion microprobe data show that Laangban hyalotekite is heterogeneous even within a given sample; the most important substitutions are Pb = Ba, K and coupled B = Si and B = Be. Minor constituents include Mn in the Laangban hyalotekite and Na in the Dara-i-Pioz hyalotekite, which also differs in its significantly higher Ba/Pb ratio. Conditions suggested for hyalotekite formation at Laangban and Dara-i-Pioz are P < or = 4 kbar, T > or = 500 degrees C, silica saturation, peralkalinity, and relatively high oxygen fugacities and low sulphur fugacities. These temperatures must have been sufficiently high to allow for miscibility of Pb with Ba (and K) despite the lone pair of electrons of Pb (super 2+) .


ISSN: 0026-461X
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 58
Serial Issue: 2
Title: Hyalotekite from reedmergnerite-bearing peralkaline pegmatite, Dara-i-Pioz, Tajikistan and from Mn skarn, Langban, Varmland, Sweden; a new look at an old mineral
Affiliation: University of Maine, Department of Geological Sciences, Orono, ME, United States
Pages: 285-297
Published: 199406
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 38
Accession Number: 1994-041527
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 6 tables
N36°00'00" - N41°00'00", E67°00'00" - E75°00'00"
N58°52'60" - N61°02'60", E01°42'00" - E14°30'00"
Secondary Affiliation: Russian Academy of Sciences, RUS, Russian FederationUniversity of Michigan, USA, United StatesHercules Research Center, USA, United StatesAerospace Corporation, USA, United States
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
Update Code: 199419
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