A widespread genus of ammonites from the Jurassic Period of the Mesozoic Era approximately 172 million years ago.

A chemical mineral classification system. Dana's System of Mineralogy, now in 8th Edition.

A locality specifically mentioned in Dana's System, any edition, for a mineral.

A penetration twin that results from transformation.

During deformation atoms can be pushed out of place. If this happens to produce a symmetrical arrangement, it will produce a deformation twin. Calcite is easily twinned in this way.

A tendency for a mineral to lose it's water content, often altering to a different species.

Crystals with inclusions that resemble dendrites or plant like patterns.

Mineral deposit or ore deposit is used to designate a natural occurrence of a useful mineral, or an ore, in sufficient extent and degree of concentration to invite exploitation.

The word alone generally denotes vertical depth below the surface. In the case of incline shafts and boreholes it may mean the distance reached from the beginning of the shaft or hole, the borehole depth, or the inclined depth.

Specialized chemical or electronic instruments used to detect mine gases.

A phase of activity ranging from confirmation of a mineral deposit to the decision to build a mine. Development includes all geological, engineering and economic work necessary to ensure profitable mining and compliance with applicable laws.

The degree to which a material transmits light.

The hardest and most brilliant of all precious gems. Drills are equipped with diamond tips in order to cut through hard rock.

A round, disk-shaped habit, thicker in the middle than at the edges.

The inclination of a geologic structure (bed, vein, fault, etc.) from the horizontal; dip is always measured downwards at right angles to the strike.

A twelve-sided crystal in the Isometric system.

A crystal form parallel to one of the lateral axes and intersecting the other two.

An optical phenomenon of some minerals which splits rays of light into two rays.

A crystal displaying terminated faces on both ends.

A horizontal passage underground. A drift follows the vein, as distinguished from a crosscut that intersects it, or a level or gallery, which may do either.

An underground mine in which the entry or access is above water level and generally on the slope of a hill, driven horizontally into a seam.

Piercing a hole in rock. In exploration, drilling allows for samples of the rock to be taken. In mining, it is used to insert explosives for blasting.

A layer of crystals that form within a mineral crust, like the inner cavity of a geode. Amethyst crystals are often found in a druze. The inner cavity of agate geodes are often lined with a druze of sparkling quartz crystals.

(Vein) A long mass of eruptive rock, a dyke may consist of mineral deposits located between other rocks.