How are Opals made?
Opal is formed from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids , caused by natural faults or decomposing fossils. As the water evaporates, it leaves behind a silica deposit. This cycle repeats over very long periods of time, and eventually opal is formed.
It’s believed that perhaps 30 million years ago, lots of silica was released into a solution which filled cracks in the rocks, layers in clay, and even some fossils. Some of them became precious opals. It takes about 5 to 6 million years to make a 1 cm opal to mature.
Where do most Opals come from?
More than 90% of the world’s precious opals come from Australia, and the rest can be found in other parts of the world such as Mexico, Brazil, Indonesia, Czech Republic, Ethiopia and USA.
The Great Artesian Basin is one of the largest underground fresh-water reservoirs in the world. It underlies approximately 22% of Australia – occupying an area of over 1.7 million square kilometres beneath the arid and semi-arid parts of Queensland, New South Wales, South Australia and the Northern Territory. All Australian opals have been sourced from this artesian basin as the opals are made from the water. Other opals around the world have been made differently, such as the opal from Ethiopia and Mexico which is made from volcanic activity under the mountains.
What are the different types of opals?
Black opal is the most valued type of opal. White Opal and Crystal Opal. Boulder Opal. Fire Opal. Opal Doublet and Opal Triple are man made opal.
How much are Opals Worth?
Generally opals with a black or dark body tone are more valuable than those with a white, light, or crystal body tone, because a stone with a darker body tone tends to display colours more vibrantly. Each stones is as unique as the next so prices can vary. The price is usually determined by the colours that shine through the stone. Black opal is the most prized opal and may realise prices over AUD $20,000 a carat.
What is the most expensive gemstone in the world? In 2018 it’s a blue diamond costing nearly $4 million per carat, besting the previous holder, a Pink Star diamond a $1.2 million per carat. Average sale prices of the most expensive gemstones are as follows:
- Blue Diamond – $3.93 million per carat
- Musgravite – $35,000 per carat
- Jadeite – $20,000 per carat
- Alexandrite – $12,000 per carat
- Red Beryl – $10,000 per carat
- Padparadscha Sapphire – $8,000 per carat
- Benitoite – $3,800 per carat
- Black Opal – $3,500 per carat
- Demantoid Garnet – $3,300 per carat
- Taaffeite – $2,500 per carat
This determines that black opal is the 8th most expensive gemstone in the world.
Why Opals are a wise choice for Jewellers
- Australian Opals make unique and interesting jewellery
- They give your display colour and character
- Every single opal is unique, special, one and only
- Jewellery with character and colour is in very high demand
- Very good margins for profit in finished pieces
- Opals appreciate with time
Fun facts about Opals!
Opal is the birthstone of October.
Opal has been found on Mars!
The ancient Greeks believed that opals were formed from the tears of joy wept by Zeus when he defeated the titans
Queen Victoria’s favourite gemstone was Opal!