Minerals - Key terms
ALLOY:
A mixture of two or more metals.
ANION:
The negative ion that results when an atom or group of atoms gains one or more electrons.
ATOM:
The smallest particle of an element, consisting of protons, neutrons, and electrons. An atom can exist either alone or in combination with other atoms in a molecule.
ATOMIC NUMBER:
The number of protons in the nucleus of an atom. Since this number is different for each element, elements are listed on the periodic table in order of atomic number.
CATION:
The positive ion that results when an atom or group of atoms loses one or more electrons.
CHEMICAL BONDING:
The joining, through electromagnetic forces, of atoms representing different elements. The principal methods of combining are through covalent and ionic bonding, though few bonds are purely one or the other.
CLEAVAGE:
A term referring to the characteristic patterns by which a mineral breaks and specifically to the planes across which breaking occurs.
COMPOUND:
A substance made up of atoms of more than one element, chemically bonded to one another.
COVALENT BONDING:
A type of chemical bonding in which two atoms share valence electrons.
CRUST:
The uppermost division of the solid earth, representing less than 1% of its volume and varying in depth from 3 mi. to 37 mi. (5-60 km).
CRYSTALLINE SOLID:
A type of solid in which the constituent parts have a simple and definite geometric arrangement that is repeated in all directions.
ELECTRON:
A negatively charged particle in an atom, which spins around the nucleus.
ELECTRONEGATIVITY:
The relative ability of an atom to attract valence electrons.
ELEMENT:
A substance made up of only one kind of atom. Unlike compounds, elements cannot be broken chemically into other substances.
HARDNESS:
In mineralogy, the ability of one mineral to scratch another. This is measured by the Mohs scale.
HYDROCARBON:
Any chemical compound whose molecules are made up of nothing but carbon and hydrogen atoms.
ION:
An atom or group of atoms that has lost or gained one or more electrons and thus has a net electric charge. Positively charged ions are called cations, and negatively charged ones are called anions.
IONIC BONDING:
A form of chemical bonding that results from attractions between ions with opposite electric charges.
LUSTER:
The appearance of a mineral when light reflects off its surface. Among the terms used in identifying luster aremetallic, vitreous (glassy), and dull.
MINERAL:
A naturally occurring, typically inorganic substance with a specific chemical composition and a crystalline structure. Unknown minerals usually can be identified in terms of specific parameters, such as hardness or luster.
MINERALOGY:
The study of minerals, which includes a number of smaller sub-disciplines, such as crystallography.
MIXTURE:
A substance with a variable composition, meaning that it is composed of molecules or atoms of differing types and in variable proportions.
MOHS SCALE:
A scale, introduced in 1812 by the German mineralogist Friedrich Mohs (1773-1839), that rates the hardness of minerals from 1 to 10. Ten is equivalent to the hardness of a diamond and 1 that of talc, an extremely soft mineral.
MONOMERS:
Small, individual subunits that join together to form polymers.
NUCLEUS:
The center of an atom, a region where protons and neutrons are located and around which electrons spin.
ORE:
A rock or mineral possessing economic value.
ORGANIC:
At one time, chemists used the term organic only in reference to living things. Now the word is applied to most compounds containing carbon and hydrogen, thus excluding carbonates (which are minerals) and oxides such as carbon dioxide.
PERIODIC TABLE OF ELEMENTS:
A chart that shows the elements arranged in order of atomic number, along with the chemical symbol and the average atomic mass for that particular element.
POLYMERS:
Large, typically chainlike molecules composed of numerous smaller, repeating units known as monomers.
PROTON:
A positively charged particle in an atom.
PURE SUBSTANCE:
A substance, whether an element or compound, that has the same chemical composition throughout. Compare with mixture.
REACTIVITY:
A term referring to the ability of one element to bond with others. The higher the reactivity (and, hence, the electro negativity value), the greater the tendency to bond.
ROCK:
An aggregate of minerals.
SPECIFIC GRAVITY:
The ratio between the density of a particular substance and that of water.
STREAK:
The color of the powder produced when one mineral is scratched byanother, harder one.
VALENCE ELECTRONS:
Electrons that occupy the highest principal energy level in an atom. These are the electrons involved in chemical bonding.