Opal is a gemstone that is made of hydrated silica and water. It can be many colors, including white, black, red, orange, pink, and green. Opals are known for their play of colors, which change depending on the angle from which you look at them. 
Characteristics
Hardness: 5.5–6.5 on the Mohs scale 
Composition: SiO2·nH2O, meaning it's hydrated silica 
Water content: Typically 6–10% water by weight 
Structure: Amorphous, meaning it doesn't have a definite crystal structure 
Color: Can be many colors, including white, black, red, orange, pink, and green 
Play of colors: A property that causes the colors to change depending on the angle from which you look at it 
Product description:>
Stone size : 6x4,7x5 
Origin :Ethiopia