Any form of repetitive sedimentary rock stratification that was deposited within a year. This annual deposit usually consists of paired contrasting layers (varves) of alternately finer (darker) and coarser (lighter) silt or clay, reflecting seasonal variations in sedimentation (winter and summer) within the year. Varved deposits are most commonly found in glacial lakes, but they can also be found in nonglacial lakes and marine settings.
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A large body of igneous rock, having distinct crystals in a relatively fine-grained base, that contains chalcopyrite and other sulfide minerals. These deposits contain vast amounts of ore that averages a fraction of 1percnt copper by weight; although low-grade, the deposits are important because they can be worked on a large scale at low cost. Large porphyry copper deposits are worked in the southwestern U.S. (where molybdenum may be produced as a by-product), the Solomon Islands, Canada, Peru, Chile, Mexico, and elsewhere.
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Natural concentration of heavy minerals caused by the effect of gravity on moving particles. When heavy, stable minerals are freed from their matrix by weathering processes, they are slowly washed downslope into streams that quickly winnow the lighter matrix. Thus the heavy minerals become concentrated in stream, beach, and lag (residual) gravels and constitute workable ore deposits. Minerals that form placer deposits include gold, platinum, cassiterite, magnetite, chromite, ilmenite, rutile, native copper, zircon, monazite, and various gemstones.
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Receipt from a bank acknowledging the deposit of a sum of money. The most common type, the time certificate of deposit, is for a fixed-term interest-bearing deposit in a large denomination. It consequently pays higher interest than a savings account, though the investor who withdraws money before its maturity date is subject to a penalty. Introduced in the early 1960s, CDs have become a popular method of saving.
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Independent U.S. government corporation created to insure bank deposits against loss in the event of a bank failure and to regulate certain banking practices. Established after the bank holiday in early 1933, the FDIC was intended to restore public confidence in the system. It insures bank deposits in eligible banks up to $100,000 for each deposit. All members of the Federal Reserve System are required to insure their deposits with the FDIC, and almost all commercial banks in the U.S. choose to do so.
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