Tag Archives: Zircon

Discovery of Rarest Mineral Reidite in the Largest Australian Crater

Craters are circular depressions caused by the high impact of planetary bodies (meteorites, comets etc.) that crash on Earth. The arbitrary patterns that we see on the moon are actually craters. Our planet also has this geological feature but not in the abundance that we see on extraterrestrial bodies.

Besides having an extraterrestrial connection, a very few craters are known for their rich mineral content. There are around 128 small and large craters on the earth’s surface but only six of them have a noteworthy mineral presence.   

In this article, we are going to discuss one of the largest craters of our plant and how its creation led to the formation of an entirely new class of extremely rare minerals.

Woodleigh Crater: Australia’s Largest Impact Crater

Woodleigh Crater, Australia

Woodleigh Crater Region of Australia

Woodleigh Crater is located in Western Australia, created by a meteorite impact that occurred millions of years ago. It was relatively a newly found crater discovered just 19 years ago. Geologists initially estimated that Woodleigh had a diameter around 74 miles.

Later on, another research team claimed that its diameter was not more than 37 miles. The exact diameter of Woodleigh is still under research.

Even if we take the later finding into consideration, Woodleigh will still be one of the largest craters on the planet. It is indisputably the largest crater of Australia. The age of the crater is believed to be 300 million years old. In other words, 300 million years ago a meteorite collided with the terrestrial surface that now comes within Western Australia.  It was the period when the dry land is predominantly covered with plants and the evolution of sharks who just started evolving in the oceans.

Reidite Discovery in Woodleigh Crater

There are some preset geological activities associated with the discovery of any crater. At the outset, researchers try to determine the age of the discovered depression. Secondly, they try to estimate the size of the celestial body that caused it by determining the radius of the depression. In some cases, they also try to make the mineral profile of the discovered region. It depends on how much relevant authorities are interested in the given project.

Before the accidental discovery of reidite, Woodleigh Crater was also one of those sites where geologists were only trying to determine the age of the meteorite. Reidite is an extremely rare mineral only found on six sites around the world. This exceptionally rare specimen is actually a re-crystallized form of zircon, which is a widely available silicate mineral. Reidite is formed when zircon undergoes an extreme pressure change.

As we know, diamonds are formed when carbon deposits experience certain high-pressure conditions underneath. Reidite is also formed through the same process when zircon undergoes extremely high-pressure changes. However, the pressure required for the formation of reidite is exponentially higher than that of what is required for diamond formation.

Earth’s atmospheric pressure is 1 atm and reidite formation takes place at a whopping 300,000 atm. Scientists believe that geological processes going in the Earth’s crust can’t generate such tremendous pressure. This leads to the conclusion that reidite can only be formed under the great pressure and shock waves generated when a hypervelocity meteorite collides with the earth surface. The rarity of reidite and its discovery from Woodleigh Crater have also substantiated this assertion.

The rearrangement of the zircon molecules to form reidite is akin to stuffing a space dedicated for 20 people with an additional 20 more. Geologists haven’t recorded such tremendous re-crystallization with any other terrestrial mineral specimen since then.

Discovered by Chance

Reidite is a mineral so rare that there is not even enough amount of it that can be used in multiple studies. It is not a mineral for which geologists would particularly devise a prospecting plan. So, the discovery of reidite from Woodleigh was also an accidental event. Undergrad students who were studying the crater for its geological features and the connection with the meteorite actually stumbled upon a specimen that had some reidite traces.

What Does the Reidite Discovery Mean?

From a gemological standpoint, there is nothing much to say about the recent reidite discovery. The mineral is extremely rare and can’t even be prospected for the sake of collection. However, the discovery has more implications regarding the geological history of our planet and how extraterrestrial phenomena have impacted it over time.  

Possible Uses of Reidite

There are really slim chances that reidite can ever be found to have any commercial significance. Nevertheless, reidite specimens can be used for the same purposes as zircon. Reidite is 10% denser than zircon and also has better hardness measurement. This means reidite specimens would be suitable for the manufacturing of abrasives and refractories.

Crater Mining Is Not an Issue

Geologists don’t worry about crater mining while deciding the commercial viability of a mineral. Craters in Canada and South Africa have abundant deposits of nickel and gold and miners excavate these minerals from there like any other mining site. However, the lack of commercial incentive and the extremely rare nature of the mineral are major reasons for companies not wanting to spend their resources on the prospecting of reidite.

Synthetic Reidite

Scientists have also tried to synthesize reidite in labs, but they couldn’t get a completely identical specimen. Again, with no commercial value in sight, companies are not pretty much interested in creating reidite in Labs.

Zircon: the Parent Mineral of Reidite

Zircon is a silicate mineral abundantly present in the earth’s crust and has many uses. It’s fine and colored specimens are used as gemstones. Blue zircons are the most common gem-grade stones in the category. It is also found in a colorless crystallized form which is polished and faceted to produce low-priced diamond alternatives.

In addition, its opaque specimens have many commercial uses as well. For instance, the white zircon deposits are processed to make pigments and whitening agents. It is really fascinating how a meteorite impact has transformed a widely available zircon into one of the rarest geological specimens.

Zircon: From Gemstone to Pigment

Zircon gem in red

Photo by simplyyayimages.com

Zircon is a mineral compound composed of the elements zirconium and silicon. Zircon is commonly found in nearly every type of rock formations all around the world. Zircon has been used as a gemstone for millennia. Even though zircon comes in different colors but the most sought after is colorless zircon due to its close resemblance with diamonds, thanks to its fine dispersion and brightness.

Name and history of zircon

Zircon faces chronological injustice because most of the people know it as an imitation element due it its extensive use as a low-cost diamond substitute in the beginning of the 20th century. However, the stone is naturally found in many different shades. Even the origination of the name ‘zircon’ indicates that the other colors of the mineral were equally popular in the past.

Name origin of zircon

There are two popular theories regarding the name origination of this mineral stone:

  • Some historians think that ‘zircon’ is derived from the Arabic word ‘zarkun’ which translates to vermilion or cinnabar, both represents the different shades of red.
  • Other historians are of the thought that zircon is borrowed from the Persian word ‘zargun’ meaning gold colored.

With zircon’s natural occurrence in a wide variety of color shades, either of the name origination can be true.

A prized stone during medieval times

Different variants of zircons held important place during middle ages. People believed that these stone had the ability to repel evil spirits. Possessing zircon was associated with good fortunes and wisdom.  

Important ornamental stone of Victorian era

Zircon became widely popular during Victorian era. Many jewelry specimen of the time were fitted with rare blue variants of the gemstone. A famous gemologist of the time, George Kunz was known for his fondness of zircon. He even proposed the change in name of the stone to highlight its vivid characteristic.

Geology of the stone

Igneous rock formations that have undergone the process of metamorphism usually host zircon gemstone. They are also found as accessory mineral in granite deposits. Most of this zircon goes unnoticed because its aggregate are present in very small size dispersed in a larger volume of the given ore.  

Gem-grade variety of zircon can be found in the soil and sedimentary rocks. Due to their high resistance to graze and chemical reactions, they remain keep their shape and structure even when the rock formation around them undergo erosion. Therefore, there are certain billion-year old deposits of zircon as per their carbon dating. The bigger the cut of zircon, the better it would be to be used as gemstone.

Gemstone zircon

Even in modern times, zircon gemstones are used in many jewelry items. Most of the famous choices of zircon gemstone are brown, red and yellow and treated variants of green and blue. We have already discussed that colorless zircons are used as the low cost diamond substitutes. The other in-demand type of modern times is blue zircon.  

Perfect fit for jewelries’

Due to its greater value of hardness on Mohs scale (7.5) and good cleavage grading, it is suitable to be used in different ornamental items including earrings, brooches, rings and bracelets. Jewelry items featuring zircon as the primary gemstone can last for many years without losing the sheen and magnificence of the stone.

Industrial and gem-grade mining of the stone

Since the use of zircon is not limited to the domain of jewelry and gems anymore. Industrial use of zircon has also been established with time. Mining of both type of grades are usually done in separate geological sites.  

Gem-grade

Gem-grade deposits of zircon are being mined for centuries from the alluvium deposits located in the far eastern countries of Vietnam, Myanmar and Cambodia. Sri Lanka is also famous for the mining of gem-grade zircon.  

Industrial-grade

Now more mining of the stone is done for the sake of its industrial uses. Australia tops the chart for mining zircon for its industrial uses. Brazil, China and Kenya also have some noteworthy land and marine alluvial deposits of industrial-grade Zircon.

Due to its high temperature resistant characteristic, zircon is used as a refractory lining that are installed inside furnace and kilns. By converting zircon mineral into zirconium dioxide at extremely high temperature, it gets into amorphous form which is then used as a pigment in different industrial and manufacturing processes.