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Quartz aggregates revisited.
1Laboratory for Development and Methods, Condensed Matter Research with Neutrons and Muons, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland. hans.grimmer@psi.ch
Acta Crystallographica. Section A, Foundations of Crystallography
|February 21, 2006
Summary
This study examines quartz crystal intergrowths, focusing on how crystal orientations and contact planes influence twin formation. Findings suggest lattice coincidence multiplicities may correlate with the frequency of intergrowths in low- and high-quartz.
Area of Science:
- Mineralogy
- Crystallography
- Geology
Background:
- Quartz aggregates form through crystal coalescence in magma or hydrothermal solutions.
- Crystal intergrowths are classified based on contact faces and relative orientations.
Purpose of the Study:
- To analyze the crystallographic relationships in quartz intergrowths.
- To investigate the conditions leading to different types of quartz twins.
Main Methods:
- Analysis of crystallographic orientations and contact planes in quartz aggregates.
- Examination of symmetry translations and lattice coincidences.
Main Results:
- Identified specific crystallographic laws (Esterel, Japan, Sardinian, Tiflis, Zyndel-A, Samshvildo, Zinnwald, Disentis) governing quartz twin formation.
- Determined conditions for monoperiodic twins based on contact faces and orientations.
- Found that rational axial ratio squared (c/a) leads to exact 2D and 3D lattice coincidence.
Conclusions:
- The multiplicity of lattice coincidence may explain the occurrence frequency of intergrowths in low- and high-quartz.
- Understanding these crystallographic relationships is key to interpreting quartz aggregate formation.