H

Habit

The attributes of the appearance of a crystal or aggregate.

Hackly (fracture)

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

Halides

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.

Halogen

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.)

Hardness

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.)

Hardness testing kit

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

Hard water

Water rich in calcium.

HCl

Abbreviation and chemical formula of hydrochloric acid.

Heat treated

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

Hemimorphic

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

Hexagon

Polyhedron with six sides and a top and bottom base.

Hopper

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

Host mineral

Mineral that is the chief constituent of a particular rock.

Hydrate

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

Hydration

The addition of water into a minerals' chemical structure.

Hydrocarbons

Organic substances that are composed only of hydrogen and carbon.

Hydrochloric acid

(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.

Hydrofluoric acid

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

Hydrometallurgy

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.

Hydrothermal

"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.

Hydrous

Containing water, and in some cases, containing hydroxyl.

Hydroxides (subgroup)

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

Hydroxyl

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

Hygroscopic

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.

Hypothermal vein

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