『Abstract
　Both a trigonal and a monoclinic phase are present in all studied samples of greenalite and of its Mn-analogue, caryopilite. Whenever the relative orientations could be determined, the two phases were found to be in a fixed, coherent intergrowth with one phase either rotated by 180゜ (or ±60゜) relative to the other or inverted without rotation. On hk0 electron-diffraction photographs, the k = 3n reflections are sharp and are surrounded by incomplete hexagons of satellites directed along the three pseudohexagonal Y^* axes. The satellite spacings indicate a regular but irrational modulation of the conventional structure of the subcell, which varies from 23Å = 2.4bo in greenalite to 17Å = 1.7bo in caryopilite. The k ≠ 3n reflections have zero intensity at the lattice points. Outside these lattice points there is a distribution of diffuse intensity that varies from two to three ill-defined blobs to three sharper satellite or superlattice spots. Dark field and bright field electron micrographs from the hk0 patterns show three sets of intersecting fringes normal to the three pseudohexagonal Y^* axes, which can be resolved into domains consisting of a small number of six-member rings. The domain boundaries are poorly resolved, and there is considerable defect nature in the size, shape and lateral disposition of the domains. Fringes seen normal to the layers have a crinkled to sinusoidal appearance in places. A model supported by optical simulation is proposed for greenalite consisting of saucer-shaped island domains four tetrahedral rings in diameter. One extra tetrahedron is inserted into the tetrahedral sheet every eight tetrahedra to create antiphase relations between adjacent tetrahedral islands and to facilitate articulation with the larger octahedral sheet. Four-member and three-member rings joining adjacent islands may be inverted and coordinate with the octahedral sheet of the adjacent layer. The satellites around k = 3n reflections are believed due to a regular doming of the octahedral portions of the saucers and to the omission of rows of octahedral cations around the island edges. Tetrahedral islands coordinate randomly with anions of the octahedral sheet in greenalite, but more regularly in at least one sample of caryopilite having sharper k≠3n satellites. The islands in caryopilite are three rings in diameter. The relation of the intergrown trigonal and monoclinic phases to the island domains is not known.

Keywords: greenalite; caryopilite: serpentine; minesotaite; X-ray; TEM; HRTEM』

Sommaire
Introduction
Greenalite
　Electron-microprobe results
　X-ray study
　Electron-diffraction study
　Electron microscopy
Manganese-rich samples
Summary of data for greenalite-caryopilite
Interpretation
Minnesotaite
Acknowledgements
References