Dark patterns on a beach in shallow waters that are a classic example of heavy mineral sorting (often called a "placer" formation). Heavy Mineral Patterns: Dark, flame-like streaks of black and purplish sand (magnetite, ilmenite, and garnet) sorted by wave action. Quartz-Feldspar Base: A background of lighter golden-brown sand composed of quartz and feldspar grains. Hydrodynamic Sorting: Intricate shapes created by the "swash and backwash" of waves, which wash away lighter grains and leave heavier minerals behind. Sestroretsk near St.Petersburg, Russia

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