Welcome to the Mineral and precious stone glossary

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The attributes of the appearance of a crystal or aggregate.

Type of fracture resembling broken metal, exhibiting sharp, jagged surfaces. This fracture is sometimes known as "jagged" fracture

Group of minerals containing one of the halogen elements (chlorine, fluorine, bromine, and iodine) as a building block. Most halides are soft and fragile, and some are soluble in water. Many crystallize in the isometric system.

Five chemically related elements belong in the halogen group. They are astatine, bromine, chlorine, fluorine, and iodine. Minerals that are composed of the halogen elements are known as halides. (Astatine is a synthetic element and there are no minerals that contain it in their structure.)

The resistance of an object to scrapes and scratching. The harder it is, the greater its resistance. (See Hardness in mineral properties for more information.)

Kit composed of minerals or rods with labeled harnesses used to scratch a mineral to test its hardness.

Water rich in calcium.

Abbreviation and chemical formula of hydrochloric acid.

Said of a mineral or gem put under intense heat to enhance color or remove flaws.

Said of a doubly terminated crystal with two differently shaped ends.

Polyhedron with six sides and a top and bottom base.

Crystal form exhibiting an indenting, terraced, structure penetrating towards the center.

Mineral that is the chief constituent of a particular rock.

To absorb water and construct it as part of the crystal lattice.

The addition of water into a minerals' chemical structure.

Organic substances that are composed only of hydrogen and carbon.

(HCl) Corrosive acid used mainly for dissolving unwanted substances. It is a very destructive liquid and will destroy many minerals. See also nitric acid and acid test.

(HF) Corrosive acid used for the production of glass(, since it dissolves glass). It is a very destructive liquid and will some many minerals.

The separation of metals from ore or from alloys through a process in which a liquid is the primary factor, or the forming of alloys and purification of metals through a process in which a liquid is the primary factor. See also metallurgy.

"Hydro" means Water and "Thermal" means Heat. Hydrothermal solutions are solutions of hot water arising from underground sources. They may be as cool as cold water or hot as burning hot steam.

Containing water, and in some cases, containing hydroxyl.

Compounds of metallic elements combined with water (H2O) or hydroxyl (OH). The hydroxides are a subgroup of the oxide group.

Radical composed of hydrogen and oxygen. formula = (OH)

Describing a mineral that intakes and retains water from the atmosphere, and forms part of its structure. Hygroscopic minerals should be kept away from humid areas and water, and should preferably be kept in rice or silica gel which absorb moisture, since water can destroy such minerals.

Vein created at extreme depths and at a very high temperature.