A gemstone is also called a gem, Jewel, Precious stone, It is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments.
However, certain rocks (Lapis lazuli and opal) and occasionally organic materials that are not minerals (Amber, Jet, and Pearl) are also used for jewelry and are therefore often considered to be gemstones as well.
Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.
Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a lapidary or gem-cutter a diamond cutter is called a diamantaire.
Jade refers to an ornamental mineral, mostly known for its green varieties. It can refer to either of two different minerals: nephrite, a silicate of calcium and magnesium, or jadeite, a silicate of sodium and aluminium.
Color: Black, Green, Purple, Blue, White, Red, Pink, Grey, Yellow, Orange, Brown
Luster: Vitreous, Waxy
Crystal system: Monoclinic crystal system
Chemical formula: NaAlSi₂O₆
Hardness (Mohs hardness scale): 6 – 7
Mineral class: Jadeite
Amber is fossilized tree resin, which has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects. Amber is used in jewelry. It has also been used as a healing agent in folk medicine.
Color: Green, Yellow, Blue, Red, Brown, Orange
Crystal system: Amorphous solid
Hardness (Mohs hardness scale) 2 – 2.5
Transparency: Opaque, Transparent
Refractive index: 1.539 – 1.545
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al₂SiO₄(F, OH)₂. Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces.
Color: Yellow, Blue, Green, Purple, White, Brown, Red, Orange, Grey, Pink
Birthstone zodiac sign: Scorpio
Associated month: November
Crystal system: Orthorhombic crystal system
Chemical formula: Al₂SiO₄(F,OH)₂
Emerald is a gemstone and a variety of the mineral beryl colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness is classified as generally poor. Emerald is a cyclosilicate.
Birthstone zodiac sign: Taurus
Associated month: May
Crystal system: Hexagonal crystal system
Chemical formula: Be₃Al₂SiO₆