Sargent P. M. Ph. D. Thesis: Factors Affecting The Microhardness of Solids. University of Cambridge, England. 1979

has been cited by the following article:

• TITLE: Investigation Of Hardness Anisotropy In Tourmaline

  AUTHORS: M.O. Adeoye, O.O. Adewoye

  KEYWORDS: Tourmaline, Hardness anisotropy, Microhardness, Knoop

  JOURNAL NAME: Journal of Minerals and Materials Characterization and Engineering, Vol.3 No.2, October 20, 2004

  ABSTRACT: Tourmaline is a ring silicate material with a hexagonal crystal structure. Tourmaline crystal is made use of as an electronic component, e.g, as a transducer, mainly because of the anisotropy it exhibits in its properties. Microindentation technique was employed in the research reported in this paper, using a Knoop indenter, to investigate the anisotropy in the hardness of the tourmaline crystal on its two major crystallographic planes: (0001) and {10 10}. The material was found to exhibit hardness anisotropy in conformity with its rotary symmetry elements. The material was identified and analysed using various x-ray techniques, and was found to contain some impurities as expected of natural crystals. Tourmaline was found to have a Si/Al ratio of 1.4. The orientations of the crystal samples were determined by obtaining and indexing the Laue x-ray back-reflection patterns of the crystal samples.