Variation of synthetic serpentine, (Mg6-x-Alx)(Si4-x-Alx)O10(OH)8, unit cell parameters, molar volume (V), and aggregate refractive index (n) as a function of the substitution 2A13+ = Si4+ + Mg2+ were investigated for the compositions x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.50, 0.75, 1.0, 1.5, and 2.0. Regression equations relating variation in these parameters with composition are:

a = 5.3132(28) + 0.0169(87)x - 0.0219(55)x20.99

b = 9.1990(64) + 0.0425(138)x - 0.0354(71)x20.975

c = 7.3115(69) - 0.2277(254)x + 0.0553(155)x20.975

V = 205.030(255) + 9.899(.328)x0.75

n = 1.5504(5) + 0.0239(16)x - 0.0032(9)x20.99

Figures in parentheses represent the estimated standard deviation; underlined figures represent the significance of the regression coefficients. The best determinative curve for estimating serpentine composition from measured values of d002 (in Å) is: x=2.49497.1247d0028.5277; the significance of the regression coefficients in this equation is greater than 0.975. The linear variation of molar volume with composition suggests that aluminous serpentines form an ideal solid solution series.

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