Some heavy minerals contain valuable metals, such as titanium, zirconium, germanium, tin, uranium, and gold.
All these are classified as heavy minerals, and all are generally resistant to chemical weathering and mechanical erosion.
Deposits usually contain between 3 and 12 percent heavy minerals, consisting of ilmenite, rutile, leucoxene, zircon, and monazite.
Beach sands in temperate latitudes consist mainly of quartz, some feldspars, and a small percentage of heavy minerals.
Thus, it is not uncommon to find sedimentary deposits containing coarse quartz particles together with fine particles of heavy minerals.
Heavy minerals have a size distribution similar to that of quartz; they occur in silt, sand, and even larger sizes.
Black sand, accumulation of fragments of durable heavy minerals (those with a density greater than that of quartz), usually of a dark colour.
These accumulations are found in streambeds or on beaches where stream and wave energy was sufficient to carry away low-density material but not the heavy minerals.
Thus, heavy minerals resistant to weathering and abrasion concentrate in these areas, though they may be only minor constituents of inland rocks.
Ores of titanium, zircon, and such other important heavy minerals as thorium and cerium are mined near Jacksonville, Starke, and Vero Beach and in west-central Florida.
The contents of lead, heavy minerals, and organic material in the sediments began to increase at about 900 bc, which provided signals of early human-related activity.
