334 • Marine Minerals: Exploring Our New Ocean Frontier 



tem of mirrors and glass plates) into two parts that 

 travel unequal optical paths and when reunited con- 

 sequently interfere with each other. 



Invertebrate: an animal lacking a backbone and an in- 

 ternal skeleton. 



KroU Process: A reduction process for the production 

 principally of titanium metal sponge from titanium 

 tetrachoride by molten magnesium metal. 



Larvae: free-living inmature forms that have developed 

 from a fertilized egg but must undergo a series of 

 shape and size changes before assuming the charac- 

 teristic features of the adult organism. 



Laterke: Weathered material composed principally of 

 the oxides of iron, aluminum, titanium, manganese, 

 nickel and chromium. Laterite may range from soil- 

 like porous material to hard rock. 



Leucoxene: A mineral assemblage of intermediate tita- 

 nium dioxide (TiOz) content composed of rutile with 

 some anatase or sphene. Usually an alteration prod- 

 uct of ilmenite, with the iron oxide content having 

 been reduced by weathering. 



Macrofauna: animals barely large enough to be visible 

 to the naked eye and not likely to be photographed 

 from a meter or two. Average body length might be 

 about 1 mm. 



Magnetic Anomaly: The difference between the inten- 

 sity of the magnetic field at a point and the theoreti- 

 cally calculated value. Anomalies are interpreted as 

 to the depth, size, shape, and magnetization of geo- 

 logic features causing them. 



Manganese Ore: Those ores containing 35 percent or 

 more manganese. 



Manganese Dioxide: MnOj, a black, crystalline, water- 

 insoluble compound used in dry-cell batteries, as a 

 catalyst, and in dyeing textiles. Also known as "bat- 

 tery manganese." 



Manganiferous Ore: Any ore important for its man- 

 ganese content containing less than 35 percent man- 

 ganese but not less than 5 percent. There a two types 

 of manganiferous ore: (1) "Ferruginous ore" — con- 

 taining 10 to 35 percent manganese; and (2) "Man- 

 ganiferous iron ore" — containing 5 to 10 percent 

 manganese. 



Mining: The process of extracting metallic or nonmetal- 

 lic mineral deposits from the earth. The process may 

 also include preliminary treatment, such as cleaning 

 or sizing. 



MoUusk: a division of the animal kingdorri containing 

 clams, mussels, oysters, snails, octopuses, and squids; 

 they are characterized by an organ that secretes a 

 shell. 



Nekton: Free-swimming aquatic animals. 



Neutron Activation: Bombardment of a material by 

 high-energy neutrons which transmute natural ele- 



ments to gamma-ray-emitting isotopes of character- 

 istic identity. 



Ore: The naturally occurring material from which a 

 mineral or minerals of economic value can be ex- 

 tracted at a reasonable profit. 



Overburden: Loose or consolidated rock material that 

 overlies a mineral deposit and must be removed prior 

 to mining. 



P2O5 : Phosphorus pentoxide, the standard used to meas- 

 ure phosphorus content in ores and products. 



Passive Margin: The trailing edge of a continent located 

 within a crustal plate at the transition between con- 

 tinental and oceanic crust and characterized by its 

 lack of significant volcanic and seismic activity. 



Pelagic: pertaining to the open ocean. 



Perovskite: A natural, complex, yellow, brownish-yel- 

 low, reddish, brown, or black calcium-titanium ox- 

 ide mineral. 



Phosphate Rock: Igneous rock that contains one or more 

 phosphorus-bearing minerals, e.g. phosphorite, of 

 sufficient purity and quantity to permit its commer- 

 cial use as a source of phosphatic compounds or 

 elemental phosphorus. 



Phosphorite: A sedimentary rock with a high enough 

 content of phosphate minerals to be of economic in- 

 terest. Most commonly it is a bedded primary or re- 

 worked secondary marine rock composed of micro- 

 crystalline carbonate fluorapatite in the form of layers, 

 pellets, nodules, and skeletal, shell, and bone fragments. 



Phylogeny: the evolutionary or ancestral history of 

 organisms. 



Phytoplankton: the plant forms of plankton. 



Placer: Concentrations of heavy detrital minerals that 

 are resistant to chemical and physical processes of 

 weathering. 



Placer: A mineral deposit formed by mechanical con- 

 centration of mineral particles from weathered debris. 

 The mineral concentrated is usually a heavy mineral 

 such as gold, cassiterite, or rutile. 



Plankton: passively floating or weakly motile aquatic 

 plants and animals. 



Plate Tectonics: A model to explain global tectonics 

 wherein the Earth's outer shell is made up of gigan- 

 tic plates composed of both continental and oceanic 

 lithosphere (crust and upper mantle) that "float" on 

 some viscous underlayer in the mantle and move 

 more or less independently, slowly grinding against 

 each other while propelled from the rear by seafloor 

 spreading. 



Podiform-Type Deposits: Primary chromite mineral de- 

 posits that are irregularly formed as lenticular, tabu- 

 lar, or pod shapes. Because of their irregular nature, 

 podiform deposits are difficult to locate and evalu- 

 ate. Most f)odiform deposits are high in chromium. 



