Glossary of Rock and Mineral Terms - N

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nacre

The iridescent inside of a mollusk shell, which is used as an ornament. Not to be confused with pearl.

native

Composed of only a single element; not combined with any other elements.

native elements group

Group of minerals containing naturally occurring minerals with a molecular structure of only one element; examples are Copper, Sulfur, and Diamond. Also included in this group are metallic and semi-metallic alloys, which are minerals composed only of two or more metallic or semi-metallic elements of varying percentage; two examples are Iron-Nickel (Fe,Ni) and Allemontite (As,Sb). The minerals Gold and Platinum are considered native elements even though they are never 100% pure gold or platinum, containing indefinite traces of other elements, thereby causing them to be metallic alloys. The native elements may be divided into three groups: The metallic elements, The semi-metallic elements, and the non metallic elements.

natural bridge

An arch-shaped stretch of bedrock remaining in a karst region when the surrounding bedrock has dissolved.

natural glass

Igneous rocks that forms when rapid cooling of molten rock occurs. Natural glasses, such as Obsidian, are amorphous with a rounded shape, and usually contain conchoidal fractures.

natural spring

A place where groundwater flows to the surface and issues freely from the ground.

nesosilicates

Group of silicate minerals that contain only single, non-combining groups of tetrahedrons.

neutron

A particle that is found in the nucleus of an atom, has a mass approximately equal to that of a proton, and has no electric charge.

nitrates group

Group of minerals that contain one or more metallic elements plus the nitrate radical (NO3). These minerals are all fragile and soft. With one exception, they are all soluble in water, and are therefore found only in arid regions, primarily in dry lake deposits. The nitrates are a small group, and are sometimes classified as a sub-category of the carbonate group.

nitric acid

(HNO₃) Corrosive acid used in the manufacture of explosives and fertilizers. It is a very destructive liquid and will destroy many minerals.

nodular

Spherical, in the shape of a small rounded lump.

nodule

Aggregate consisting of a spherical lump, usually from groups of small crystals.

nonbrittle

not crumbling to a powder when crushed.

nonmetal

Substance that does not exhibit the properties of a true metal.

non-crystalline

Not containing any crystals;  amorphous mineral or variety of mineral.

non-metallic elements

The nonmetallic elements are minerals that belong in the native elements group and don't exhibit any metallic properties (except for Graphite, which has a metallic luster). They are light in weight and can be transparent.

normal fault

A dip-slip fault marked by a generally steep dip along which the hanging wall has moved downward relative to the footwall.

nuclear fission

The division of the nuclei of isotopes of certain heavy elements, such as uranium and plutonium, effected by bombardment with neutrons. Nuclear fission causes the release of energy, additional neutrons, and an enormous quantity of heat. Nuclear fission is used in nuclear power plants and nuclear weapons. A by product of nuclear fission is toxic radioactive waste. See also nuclear fusion.

nuclear fusion

The combination of the nuclei of certain extremely light elements, especially hydrogen, effected by the application of high temperature and pressure. Nuclear fusion causes the release of an enormous amount of heat energy, comparable to that released by nuclear fission. The principal by product of nuclear fusion is helium.

nucleus (plural nuclei)

The central part of an atom, containing most of the atom's mass and having a positive charge due to the presence of protons.

nuée ardente

A sometimes glowing cloud of gas and pyroclastics erupted from a volcano and moving swiftly down its slopes. Also called a pyroclastic flow.

nugget

Compact, waterworn, amorphous mass, found in placer deposits.

numerical dating

The fixing of a geological structure or event in time, as by counting tree rings.