montmorillonoidadj.n.
/ˌmɒntməˈrɪlənɔɪd/, U.S. /ˌmɑn(t)məˈrɪləˌnɔɪd/ Mineralogy.
A. adj.
Designating or relating to a group of clay minerals that comprises montmorillonite (in the strict sense) together with chemically related minerals which undergo a reversible expansion on absorbing water and have a characteristic structure in which water molecules are situated between sheets composed of two layers of silicon atoms sandwiching one nominally of aluminium, the differences between the minerals consisting in the extent and nature of the replacement of silicon and aluminium by other elements.
ΚΠ
1951 Clay Minerals Bull. 1 195 To avoid this confusion and also the lengthy term ‘minerals of the montmorillonoid group’..the term ‘montmorillonoid’ was suggested [by D. M. C. MacEwan].
1955 Trans. Faraday Soc. 51 582 Considerable attention has been paid in recent years to the retention of organic molecules by clays of the montmorillonoid group.
1966 Canad. Jrnl. Soil Sci. 46 235 Montmorillonoid minerals are sometimes more abundant in the lower horizons of soils in which other clay minerals are more uniformly distributed.
1971 Clay Minerals 9 107 Results of..analyses confirm the general montmorillonoid character of the mineral.
B. n.
A member of the montmorillonoid group; the group itself. Cf. smectite n.
ΘΚΠ
the world > the earth > minerals > types of mineral > silicates > phyllosilicate > [noun] > smectites
montmorillonite group1938
montmorillonoid1951
smectite1955
1951 Clay Minerals Bull. 1 195 The term ‘montmorillonoid’ was suggested [by D. M. C. MacEwan] for this group of minerals.
1953 Jrnl. Soil Sci. 4 233 It is fairly simple to detect by X-ray diffraction the presence of montmorillonoids in clays using glycerol..or ethylene glycol.
1983 Jrnl. Sedimentary Petrol. 53 395 Montmorillonoids..are enriched relative to illite.
This entry has been updated (OED Third Edition, December 2002; most recently modified version published online March 2022).
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adj.n.1951