Skip to main content

Centenary of the Australian opal: the rainbow effect


A hundred years ago, on May 8, 1915, the first piece of opal was found in Australia. Willie Hutchinson was prospecting for gold with his father in a desert town called Coober Pedy when he found a few pieces of whitish iridescent rainbow-coloured stones. Coober Pedy is now the “opal capital of the world.” It produces 80% of the world’s opals (BBC, May 8, 2015).

A group of international geologists hope to legally define the opal, Australia’s national gemstone, as a Global Heritage Stone Resource (GHSR) in order to recognize and preserve the opal’s significance in human culture. No stone has yet been designated a GHSR status.

Initially the geologists wanted to recognize specific construction rocks, such as Portland stone, Carrara marble, Sydney sandstone, and Norwegian larvikite. They want to designate and protect particular stones and rocks for conservation. But when the opal was added to the list, it was a controversial decision, even amongst geologists. Some stated that opal was not a construction stone because it was processed as jewellery.

The centenary of opals aims to highlight the magnificence of their geological context. They result from the Eromanga Sea that covered central Australia about 100 million years ago – it was the great central sea. Opals in Coober Pedy are derived from sedimentary effects. Acidic fluids dissolved silica from sandstone rich in quartz, which gives the stone iridescence – a rainbow effect. Opals found in other locations originate from volcanic events, not sedimentary settings.


The Global Heritage Stone Resource project commenced in 2008. The project has not yet designated its first status to any stone – but the honour is likely to go to Portland stone, the cream coloured building limestone found in quarries in Dorset on the south coast of England. St. Paul’s Cathedral and Buckingham Palace in London are constructed from Portland stone, and so is the United Nations building in New York. So the opal, a controversial choice, may take another hundred years before it makes the GHSR status as a heritage stone.





MARTINA NICOLLS is an international aid and development consultant, and the author of:- The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
Labels:

Comments

Post a Comment

Popular posts from this blog

The acacia thorn trees of Kenya

There are nearly 800 species of acacia trees in the world, and most don’t have thorns. The famous "whistling thorn tree" and the Umbrella Thorn tree of Kenya are species of acacia that do have thorns, or spines. Giraffes and other herbivores normally eat thorny acacia foliage, but leave the whistling thorn alone. Usually spines are no deterrent to giraffes. Their long tongues are adapted to strip the leaves from the branches despite the thorns. The thorny acacia like dry and hot conditions. The thorns typically occur in pairs and are 5-8 centimetres (2-3 inches) long. Spines can be straight or curved depending on the species. MARTINA NICOLLS is an international aid and development consultant, and the author of:- Similar But Different in the Animal Kingdom (2017), The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Suda...
1 comment
Read more

Hop on hop off bus tourism comes to Tbilisi, Georgia

City Sightseeing buses have arrived in Tbilisi. The iconic red double-decker buses, a feature of many cities around the world since the company was established in Seville, Spain in 1999, is now in six continents and almost 100 cities. The company established its Tbilisi business in November 2013, with its operations commencing in February 2014. The 90-minute tour stops at 11 major locations in Tbilisi (with 2 to 5 minute waiting times at each location): the Old City (where it commences), Freedom Square, Rose Revolution Square, Marjanishvili Square, the Dry Bridge, Konka, Avlabari, Metekhi, Akhundov Museum, the Sulfur Baths, and European Square. Passengers can hop off at any stop and see the sights, hopping back onto the next bus at any time. Alternatively, passengers can remain on the bus for the whole tour and take photographs when the bus stops at each location. There are one day (24-hour) passes (for 35 lari – about $20) and 48-hour passes for 55 lari, with family d...
2 comments
Read more

Pir-E-Kamil - The Perfect Mentor by Umera Ahmed: book review

The Perfect Mentor pbuh  (2011) is set in Lahore and Islamabad in Pakistan. The novel commences with Imama Mubeen in medical university. She wants to be an eye specialist. Her parents have arranged for her to marry her first cousin Asjad. Salar Sikander, her neighbour, is 18 years old with an IQ of 150+ and a photographic memory. He has long hair tied in a ponytail. He imbibes alcohol, treats women disrespectfully and is generally a “weird chap” and a rude, belligerent teenager. In the past three years he has tried to commit suicide three times. He tries again. Imama and her brother, Waseem, answer the servant’s call to help Salar. They stop the bleeding from his wrist and save his life. Imama and Asjad have been engaged for three years, because she wants to finish her studies first. Imama is really delaying her marriage to Asjad because she loves Jalal Ansar. She proposes to him and he says yes. But he knows his parents won’t agree, nor will Imama’s parents. ...
1 comment
Read more