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Minerals: What makes them special?

What makes a mineral valuable? Well, there are various factors to consider. The first question to ask is, “is this sought after?” It makes sense that minerals that a lot of people want are going to sell for more. So, then you need to ask why are they so sought after? One of the most obvious reasons is its rarity, which seems simple, but once you look deeper, it isn’t quite so simple. When you consider its location, size, appearance, when it was found, and who found it, rarity becomes more of a mathematical equation. By this logic, the most valuable minerals are large with no imperfections, aesthetically pleasing, and hard to find.

Ultimately, when it comes down to it, it’s all personal preference. Many collectors have specimens in their collections that may not seem overly special but have sentimental value or are simply nice to look at. Remember, value doesn’t just mean a high price tag!

Part 2 of our Watt Family Mineral Collection Auction ends this Sunday. We have several sought-after minerals, including malachite, agate, fluorite, and rhodochrosite. Keep reading to find out more about these fascinating minerals (click the images to view the lot in our catalogue).


Malachite is a copper ore commonly found in fractures and spaces deep in the ground. It gets its name from the Mallow plant, whose leaves malachite resemble. The copper in malachite gives it its distinctive green banding/rings.

Where there are malachite deposits, azurite, chrysocolla, cuprite, goethite, and calcite can often be found as well.

Malachite has been utilised for centuries, with evidence that it was mined and smelted in Israel over three thousand years ago. Typically, it’s used as an inexpensive substitute for jade in jewellery and ornaments. And, until the 1800s, it was used as a green pigment for painting.



Agate is pretty similar to quartz, with their physical properties being almost the same. Agate comes in many colours and patterns, but to be genuine agate, it must have banding. It is often found in neutral greys, whites, and browns, with purples, blues, and greens very uncommon. In fact, most commercial agate is artificially coloured to increase its value for ornaments and jewellery.

Agate is usually formed in cavities in eruptive rocks or ancient lavas. As the lava solidifies, bubbles form and create cavities. Eventually, water and silica find their way into the cavity, becoming silica gel. From there, it hardens and crystalises into quartz or chert. The colour and banding come from iron in the surrounding rock seeping into the silica gel.


Fluorite (AKA Fluorspar)

Known as “the world’s most colourful mineral,” fluorite is one of the most popular collectable minerals, second only to quartz. It comes in so many colours, in fact, that teachers often use it to show students how colour is only part of mineral identification and cannot be relied on solely. It is commonly compared to amethyst, as they have incredibly similar colours.


Fluorite can also be found in blue, green/yellow, pink, yellow, green, amethyst, purple, clear, and rainbow. Purple is the most common colour, blue and yellow are rare, and pure fluorite is colourless.

Fluorite is vital to the world as we know it. It is used to manufacture enamel, glass, ceramics, optical lenses, cement, hydrofluoric acid, concrete hardeners, toothpaste, refrigerants, lubricants, non-stick coatings, medicine/anaesthetic, stain repellent, herbicides, dyes, and more. While fluorite has many uses, it is rarely used in jewellery as it is sensitive to sudden changes in temperature, making it hard to facet. Native Americans in the United States used to carve artifacts out of fluorite.

As a widespread mineral, fluorite is found worldwide, with the largest amount in Russia, England, China, Morocco, Switzerland, South Africa, Namibia, Mexico, Canada, India, Spain, and the United States. Usually, fluorite will be found amongst galena, pyrite, chalcopyrite, marcasite, barite, sphalerite, calcite, quartz, and amethyst. Emerald-green fluorite can be found in New South Wales, while a blue variety can be found exclusively in England.



The name fluorite derives from the Latin word “fluere”, meaning “to flow.” This name is quite fitting because, In 1797, when it was being named, it was mainly used as flux (removes impurities and changes the fluidity for smelting) for steel and aluminium processing. Fluorite is also the origin of quite a few other words, including fluorescence, which is a defining trait of fluorite. Fluorite was one of the first fluorescent specimens studied, which is how it got its name. They followed the same naming method as opal/opalescence.

Typically, its fluorescent colour is blue but can also be yellow, green, red, white, and purple. Interestingly, it can fluoresce two colours simultaneously under shortwave and longwave UV light. Some fluorite is even phosphorescent, meaning it can have a third colour.

Rarely fluorite can even be thermoluminescent, meaning it glows when heated – warmth from the hands can be enough! Interestingly, this can only happen once for a specimen, so once its thermoluminescence is seen, it can never be seen again.



Rhodochrosite is a pink manganese carbonite nicknamed “bacon stone” due to its alternating pink and white banding. The faceted gems are entirely transparent, pink, red, or orange. As it’s one of the softest minerals, when used in jewellery, the way it will be worn is a vital factor to consider. 


It has been for carving and ornaments for a very long time. The Incas even considered this stone sacred as it was believed to be their gods and royal ancestors’ solidified blood.

Rhodochrosite exists worldwide, including in Argentina, Romania, Yugoslavia, Germany, and Mexico. It can also be found in Australia in New South Wales, Victoria, South Australia, and Tasmania. It is often associated with silver ore deposits.


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