Figure 4. Placering effects (see Fig. 3) on temper sand compositions as displayed on a triangular plot of the QF­ FS-OO population, representing mineral grains only (proportions recalculated exclusive of polycrystallinepolyminerallic lithic fragments), where QF = quartz and feldspar, FS = ferromagnesian silicates (clinopyroxene, orthopyroxene, hornblende, oxyhornblende, olivine, biotite, epidote), and 00 = opaque iron oxide grains (dominantly magnetite but also including maghemite, ilmenite, hematite, chromite in some cases). Placer concentration proceeds downward from the QF pole (grains of lowest specific gravity) along trends defined by lines connecting non-placer and placer variants of local temper suites, and in some cases pursues further trends toward the 00 pole (grains of highest specific gravity).