Accurate determination of the cell dimensions of magnetite

Abstract

SummaryAn analysed magnetite from Bisperg, Säter, Dalecarlia, Sweden, gave the formula , which corresponds closely to the ideal composition. A precise determination of the cell dimensions gave a 8·3963±0·0005 Å. at 18° C. Gentle heating of the powdered magnetite in evacuated silica glass tubes, before X-ray examination, resulted in sharply defined lines with high Bragg angles; an improvement which enabled precision data to be obtained. Four other new analyses of magnetites are also given and their lattice parameters are determined in the same way and are found to range from 8·3960 Å. to 8·3970 Å. The Bisperg magnetite being the purest sample examined, the value of its cell edge is taken as representative of pure magnetite.The effect of the different ionic substitutions on the cell dimensions of natural magnetites is discussed. An attempt is also made to explain the great variations among the published values of cell dimensions of artificial preparations; one main reason being the presence of defect structures with varying oxygen contents in excess of the formula requirements.

Petrology of the leucite‐bearing lavas in New South Wales∗

“…Extrapolation of measurements of the X-ray high-angle reflections (Nelson & Riley, 1945), obtained for magnetite concentrates from BEH-A and B, give cell edges of 8.482A and 8.486A (±0.002), respectively. These values are well above the cell edge for the Bisperg magnetite (Basta, 1957) and suggest significant Fe 2 TiO 4 content in solid solution.…”

Iron-titanium oxides in Some New Zealand ironsands

“…Using the graph relating molar composition and Basta's (1953) cell dimensions for hematite and ilmenite (Vincent et al, 1957, fig . 6), the ilmenite content of the rhombohedral phase is not more than 7% by weight, close to the value for the amount of ulvospinel in the corresponding unoxidised titanomagnetite (No.4, Table 3).…”

Magnesian Borates and Associated Minerals in the Cacova Ierii Skarn Deposit (Apuseni Mountains, Romania)

“…The cell parameters, calculated for nine different samples by least squares, using 12 to 17 unambiguously indexed X-ray powder reflections in the 2q range of 10 to 100°, vary between 8.371 (4) 8.400(2) Å. These values remain close by that one given by Basta (1957) for the stoichiometric magnetite (a = 8.396 Å), but suggest chemical variability of the analyzed samples. Electron-microprobe analyses of samples of magnetite I (in equilibrium with ludwigite) confirms this assumption.…”