Texture formation and element partitioning in trapiche ruby

Based on textural and compositional investigations on ruby single crystals showing textures with six arms and six growth sectors (trapiche ruby), it h as been analysed how the unique texture was formed, and the element partiti oning was governed by the growth mechanism. The arms were formed earlier by dendritic growth an rough interfaces, and the growth sectors by lateral gr owth on smooth interfaces. The arm portions consist of plural mineral phase s but show a low and almost uniform Cr content in corundum throughout the e xtension of the arm and its branches, whereas the growth sectors are single ruby phase, but show Cr zoning parallel to the growth surfaces. Element pa rtitioning in the earlier dendritic gowh is governed by thermodynamic param eters, whereas that of the latter layer-by-layer growth by kinetics. (C) 19 99 Elsevier Science B.V. All rights reserved.