Abstract
The principal mode of occurrence of hematite and ilmenite in emery ores from a number of localities is in the form of unique exsolution intergrowths, suggesting unusual crystallization-temperature-solution conditions. Magnetite, not a component of these exsolution intergrowths, is the most abundant opaque constituent in some polished sections, but is rare, or totally absent, in others, Ilmenite exsolves from hematite to sharp magnetite-hematite boundaries, showing that much of the hematite now present crystallized originally as hematite, and is thus not a later replacement product of magnetite. Some replacement of magnetite by hematite is noted, but only a minor percentage of the total hematite present has formed in this manner.
Ilmenite of one age often exsolves parallel to two crystallographic directions within hematite. In addition, two readily distinguishable ages of exsolution ilmenite in hematite are often observed. The ilmenite bodies of each age have a characteristic orientation in the hematite. The original solid solution varied in composition from dominant hematite to dominant ilmenite.
Exsolution of hematite from corundum is well shown in some sections. In those ores in which the corundum exhibits parting, hematite exsolved both as blebs and as needles, and in the ores in which the corundum does not exhibit parting, hematite exsolved only as minute blebs.
