Semi precious category there are 4 types of stones

• Topaz
• Tourmaline
• Spinel garnet
• Quarts

Topaz

Topaz gem are mainly comes from Sri lanka, brazil and other African countries. Most of the Sri Lankan topaz comes in fully white. Sri Lankan topaz has big demands in the international market because of the treatment process is very easy with sti lankan topaz. In Other countries natural topaz comes in various color ranges such blue, green, yellow, orange, red, pink, and purple. Colorless topaz often treated to give it different colors.

Chemical Formula Al2SiO4(F,OH)2
Color White, Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Multicolored
Hardness 8
Crystal System Orthorhombic
Refractive Index 1.610 – 1.638
SG 3.4 – 3.6
Transparency Transparent
Double Refraction .014
Luster Vitreous
Cleavage 1,3 – basal
Mineral Class Topaz

• Imperial Topaz – Lustrous golden orange-yellow, orange-brown, or orange-pink variety of Topaz and is its most valuable gem form.

• London Blue Topaz – Topaz with a deep sky-blue color. It is darker in tone than Swiss Blue Topaz.

• Rutilated Topaz – Topaz with yellow needle-like inclusions of the mineral Limonite. Rutile Topaz is very similar in appearance to Rutilated Quartz, hence the name Rutile Topaz. However, the name is a misnomer, since unlike Rutilated Quartz which has inclusions of the mineral Rutile, the inclusions of Rutile Topaz are not Rutile but rather Limonite.

• Swiss Blue Topaz – Topaz with a sky-blue color. It is lighter in tone than London Blue Topaz.

• White Topaz – Colorless form of Topaz.

Tourmaline

Tourmaline has range or colors like sapphires . It occurs in all colors such as pink, red, green, blue and multicolored are its most well-known gem colors. Scientifically, tourmaline is not a single mineral, but a group of minerals related in their physical and chemical properties.

• Rubellite tourmaloine – is a name for pink, red, purplish red, orangy red, or brownish red tourmaline, although some in the trade argue that the term shouldn’t apply to pink tourmaline.

• Indicolite – dark violetish blue, blue, or greenish blue tourmaline.

• Paraíba – violetish blue, greenish blue, or blue tourmaline from the state of Paraíba, Brazil.

• Parti-colored tourmaline displays more than one color. One of the most common combinations is green and pink, but many others are possible.

• Watermelon tourmaline is pink in the center and green around the outside. Crystals of this material are typically cut in slices to display this special arrangement.

Chemical Formula Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.
Color White, Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Multicolored
Hardness 7 – 7.5
Crystal System Hexagonal
Refractive Index 1.616 – 1.650
SG 2.9 – 3.3
Transparency Transparent to Opaque
Double Refraction .018
Luster Vitreous
Cleavage 3,2
Mineral Class Tourmaline

Spinel

Spinel ( /spɪˈnɛl/) is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4 in the cubic crystal system. Its name comes from Latin “spina” (arrow).[1]
Though spinels are often referred to as rubies, as in the Black Prince Ruby, the ruby is not a spinel. Balas ruby is an old name for a rose-tinted variety of spinel.

Category • Oxide minerals
• Spinel group
• Spinel structural group
Formula
(repeating unit)
MgAl2O4
Strunz classification 4.BB.05
Crystal system Cubic
Crystal class Hexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space group Fd3m (No. 227)
Unit cell a = 8.0898(9) Å; Z = 8
Identification
Color Various; red, pink, blue, lavender/violet, dark green, brown, black, colourless
Crystal habit Octehedra or flat triangular plates caused by twinning
Twinning Common
Cleavage None
Fracture Conchoidal
Mohs scale hardness 7.5–8.0
Luster Vitreous
Streak White