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A B C D E F G H I J
K L M N O P Q R S T
U V W X Y Z
- Habit the characteristic crystal form displayed by a mineral. Habit may vary with locality.
- Haematite R.I. 2-9 --- 3-22; S.G. 4-9 to 5-3; H. 5.5 to 6.5; Trigonal; Colour, black; Localities, England, Germany, Scandinavia and U.S.A. Sometimes used to imitate the black pearl. The name hematite should not be used for the heliotrope variety of chalcedony.
- Half-facets see break facets.
- Hambergite R.I. 1-55--- 1-62; S.G. 2 to 3-5; Rhombic; Colourless; Locality, Madagascar.
- Hardness the relative ability of one type of stone to wear on another type of stone. Scale of 10 as hardest to 1 as softest.
- Hardness (H) points or pencils small conical fragments of minerals set in a pencil-shaped holder for ease in testing the hardness of a stone.
- Diamond (10)
- Sapphire (9)
- Topaz (8)
- Quartz (7)
- Feldspar (6)
- Harlequin opal; see Opal.
- Hauynite a blue minera1 of cubic symmetry, it is a sodium aluminium silicate and is one of the constituents of Lapislazuli; also known as Hanyne.
- Hawk's-eye quartz pseudomorphous after crocidolite (blue asbestos) which has not suffered oxidation. See also Crocidolite.
- Heat treatment the controlled heating of certain stones, such as zircon and topaz, in order to effect a change of colour. See Chart 178.
- Heavy liquids liquids having a high density and suitable for the determination of the specific gravity of gem-stones. See Chart 118.
- Heliodor yellow beryl.
- Heliotrope see Chalcedony.
- Hematite see Ha'matite.
- Hemihedral forms those crystals which show only half the number of faces required to conform to the symmetry of the normal crystal.
- Hemimorphism the peculiarity possessed by certain crystals, presenting different forms at opposite ends of an axis of symmetry.
- Herderite R.I. 1 59-1 62; S.G. 3 0; H. 5; Greyish; Monoclinic; Saxony and U.S.A.
- Hessonite see Garnet, Grossular.
- Hexagonal one of the crystal systems. see Chart 111.
- Hexagonite see Tremolite.
- Hiddenite see Spodumene.
- Hippopotamus ivory an ivory obtained from the canine teeth of the hippopotamus. (Hippopotamus amphibus).
- Holohedral forms those crystals which show the full number of faces for the full symmetry of the system.
- Homogeneous the term used for material which is composed of similar parts of elements. It is uniform throughout.
- "Honan jade" an Oriental name variously applied to a jade and quartz mixture, or to serpentine or soapstone.
- "Hope sapphire" a MISNOMER ( COMMERCIAL LABEL ) that was suggested for the synthetic blue spinels that were the outcome of experiments in the production of synthetic blue corundum. The use of magnesia as a flux to cause even distribution of the blue colour gave the unexpected result that spinel was produced and not corundum.
- Hornblende a rock-forming mineral similar in composition to nephrite, may be black or green (Smaragdite).
- "Hot Springs diamond" a MISNOMER ( COMMERCIAL LABEL ) for rock crystal.
- Howlite an opaque white ornamental stone veined with black consisting of an aggregate of monoclinic (?) crystals; R.I. 1-59; S.G. 2-58; H. 3.5; has been stained a turquoise-blue colour; California.
- "Hungarian cat'seyes" an unsatisfactory name for quartz cat's-eyes from Bavaria.
- Hungarian opal the name applied to opal from the Cervenica mines, Hungary.
- Hyacinth name applied to the orange-red zircon or to the similarly coloured hessonite garnet. An obsolete name.
- Hyalite see Opal.
- Hydrochloric Acid a powerful mineral acid formed by the solution of the gas HCI in water. One of the constituents of aqua regia.
- Hydrogrossular correct name for the massive grossular garnet, which see.
- Hydrometer an instrument for determining the density of liquids.
- Hydrophane see Opal.
- Hydrostatic weighing the direct weighing method for determining specific gravity. See Chart 117.
- Hydrothermal method a method of growing crystals by the use of a saturated water solution at a pressure of 1,000 atmospheres and temperatures of less than 400 C. An autoclave is used in this process.
- Hypersthene R.I. 1-67-1-68 to 1-69 --- 1-70; S.G. 3-3 to 3-4; H. 5 to 6; Rhombic; Colour, dark with metalloidal iridescence. Hypersthene is related to enstatite an intermediate form being bronzite.