Absorption spectrum
The light of certain wavelengths is absorbed more strongly depend on material and produce dark line or gaps when passed trough the colored stones it can be seen when viewed with the spectroscope. It is used for identification.

Agate
Varity of Chalcedony, have banded structure in different layer of color.
Hardness : 7 Refractive Index : 1.53 Density : 2.6

Alexandtrite
Name of a gemstone, which changes color in different light from red (artificial light) to green (daylight) it is Varity of chrysoberyl.
Hardness : 7.5 Refractive Index : 1.75 Density : 3.71-3.75

Allochromatic minerals
If chemically pure under normal circumstances a colorless mineral. Often show a range of colors due to the presence of coloring elements (sample:managanese,cobalt, nickel, chromium, titanium). Minerals are Corundum, quartz, beryl, spinel.

Alloy
A combination of two or more metals, or a chemical and metal. Always used for the jewelry production

Alluvial
Sediment deposits of gems in river bed, lakes, sea and on the foot of mountains and slopes.

Almandite
A brownish red Garnet due to iron and aluminum. From mining areas like India the color change to be violet.
Hardness : 7.5 Refractive Index : 1.76-181 Density : 3.92-4.17

Ambalogynite
Colorless to golden yellow Gemstones. Not very common and not used in the jewelry industry.
Hardness : 6 Refractive Index : 1.61-1.636 Density : 3.02

Amber
Is the resin of fossilized pine tree many millions of years old. Amber from Baltic sea 20-40 million
Hardness : 2-2.5 Density : 1.06-1.10

Amethyst
Quartz from light to dark violet. It is the most popular stone of the Quartz group. The name Greek means "not drunken". Amethyst was used as a charm against drunkenness.
Hardness : 7 Refractive Index : 1.548 Density : 2.63-2.65

Ametrine
A member of the quartz group the name is a combination of Amethyst (ame) and Citrine (trine) same as the color.
Hardness : 7 Refractive Index : 1.54 Density : 2.65

Amorphous (amorphous)
Literally-without shape. Minerals without regular arrangements of atoms and consequence no regular crystal structure.

Andalusite
Collector stone in the color range green to red brown
Hardness : 7-7.5 Refractive Index : 1.64 Density : 3.18

Angstroem unit
Unit to measure wavelengths for visible light and most X-rays. A=0.000001 mm

Anisotropic
The term for cyrystals where the optical poperty vary with the direction. Like in the cubic system and show double refraction.

Annealing
Heat treatment of metal up to critical temperature during working process to release stress from cold working.

Anodizing
Dying a surface of metal by immerse it in an oxide bath. Further treatment washing and immersion in organic dye followed by final washing and sealing.

Apatite
Collector stones occasional used for jewelry production Available in many colors.
Hardness : 5 Refractive Index : 1.64 Density : 3.15

Aquamarine
A Beryl varity, range from light blue to greenish blue color.
Hardness : 7.5-8.00 Refractive Index : 1.575-1.583 Density : 2.69

Assaying
Testing precious metal with the help of chemicals to determine the purity (%) to the norm standards.

Assembled gemstones
Altered gemstones to improve they appearance and quality. Alterations (backfoil, backing, doublets, triplets)

Asterism
The star like effect are a reflection of light from the inclusion, seen only on suitable stones, which are cut to cabochons with the inclusions in the correct directions.

Atom
The smallest part of an element which retain the properties of it.

Atomic weight
The weight of an atom compared to the weight of an atom of oxygen,16.

Avoirdupois
The weight system of most English speaking counties. 16 ounces to the pound avoirdupois.

Axnite
Collector stone, reddish brown color and violet colors. Mostly flat stones found.