Opal is a hydrated amorphous form of silica. Opal also contains few trace elements like Fe, Al, Ca, Mg & Na. water percentage is variable in Opal stones. Colors of Opal range from Colorless to Blue, Orange, Red and Green to Black. Few Opals exhibit a distinct phenomenon of Light called Diffraction due to its internal structure. The entering light diffracts into different colors resulting in the appearance of rainbow colors on its surface. This appearance of Rainbow colors is referred to as ‘Play of Color’ effect, also called ‘Fire’ in Opal. This phenomenon is common to Diamonds also. Due to this vivid similarity in optical property, Opal is considered as an alternative stone for the diamond in Indian astrology. White Opal with Fire is worn as an alternative for Diamond as per astrology. Intensity of Fire and Surface Finish defines the quality of Opal. Opal is a softer stone as compared to Sapphire and Emerald. Opal Contains water and any sudden changes in temperature may cause it to crack or fracture.
Quality of Opals is adjudged mainly by its – Body Color, Luster, Surface Finish, Optical effect and Carat Size. ‘Fire’ is the name given to the phenomenon of light; Rainbow colors on its surface, often referred as ‘ the interplay of colors’. Fire adds Life, Beauty and Power to the Opal Stone. An Opal without fire is lifeless and looks like a plain marble. As the Fire increases, the price of Opals increases. The Best source of Opal is Australia. Opal comes in various colors like Red, Blue, Green, white and Black. But White Opal is most desired as the fire complements the white Base Color of Opal. A good Quality cut-&-polished opal should have good Luster on its surface. The Surface of Opal should not have Cracks, Linings or Spots. It is very common to have spots or patches on Opals which brings downs its price. Opal is a softer Stone as compared to other stones; hence check for any chipping or breakage in the stone carefully while buying.
Opal is an Isotropic (Singly Refractive) Mineral. Chemically, Opal is hydrated silica. Opal is amorphous. Hardness is 5.5 – 6.5 on Moh’s scale. Refractive Index (RI) range of opal is 1.44 – 1.47 & Specific Gravity (SG) is 1.98 – 2.20. Opal is considered a very good Astrological substitute for Diamond stone worn for Venus planet ( Shukra ). Wear only Certified Natural Opal stone for best astrological results. Major sources of opal are Australia, Ethiopia & Mexico. Australian Opals are considered best.