The opal is and will actually always be one of the most beloved and also unique gemstones, which are truly appreciated for its beautiful and especially unique and deep colours. We know there is confusion regarding the nature of the opal, the reason? In the world of opals, we mostly hear the question travel is opal a type of glass?
The answer to the question may seem incredibly easy but may be more complicated than you would actually expect. Together with you, we will take a closer look at the properties of opal, we will additionally talk about opal glass. This is to outline the full place.
What is opal?
We know that opal is a natural gemstone, which in its basic principles is incredibly different from many other gemstones such as, for example: diamond, ruby or sapphire. Unlike these stones, which have crystalline structures, opal is amorphous silica (SiO₂-nH₂O). This means it has no solid, ordered crystal structure. Instead, opal consists of microscopic spheres of silica arranged in a network, which gives it its unique properties.
As a rule, the silica spheres are so small in shape that they can play with the light entering the stone. This creates that well-known "play of colours". It is a phenomenon also known as opalescence, it basically causes the opal to reflect different colours, this depends entirely on the angle of incidence and from which angle you are looking.
We know that opal additionally contains a considerable amount of water, this could even range from 3% to 21%. This makes opal so notorious and also so vulnerable regarding drying out and cracking than many other stones.
What is glass?
We know better than anyone else what glass actually is. It is so woven into our daily lives that we can't really ignore it. But did you know that glass has incredibly interesting properties that distinguish it from crystalline substances such as minerals, for example? Glass, like an opal, is an amorphous material, it means it has no ordered internal structure. Glass is formed by heating silicon dioxide (SiO₂, or sand) until it melts, often together with other substances such as soda (sodium carbonate) and lime (calcium carbonate), after which it is rapidly cooled so that the atoms have no time to form a crystal structure. So we now know that glass and opal are amorphous and largely composed of silica. This does not make it strange to compare these two materials. However, there are clear differences when we take a closer look at this.
What properties do opal and glass have?
If we really want to be able to clearly answer the question of whether opal is a type of glass, we must first compare the properties of the two materials side by side:
Structure and composition
We already know, for example, that glass is a man-made product and opal is slowly created naturally through a process of millions of years. We create glass by heating sand and also other additives at as much as 1700°C, which breaks down the solid crystal structure of sand and creates an amorphous liquid that turns into glass when cooled. We also know that glass is often seen as an unfinished solid, so it does not have an organised structure like a crystal.
Opal is at all times a naturally formed mineral, we just indicated this, of course. An opal consists, as it were, of a whole bunch of microscopic spheres of amorphous silica. These are all arranged in a specific way. These spheres are generally between 150 and 300 nanometres in size and are entirely responsible for the optical effects in opal. These therefore cause the well-known "Play of Colours". Funnily enough, these spheres are completely textured, so this is not the case with glass. It's funny to think about the fact that opal can naturally get a structured lattice and glass, something that is man-made, absolutely not.
Colour play and optical properties
A truly recognisable feature of opal, something that makes it so sought-after and praised, is its vibrant play of colours. This is thus created by the microscopic silica spheres in the stone. When light hits the spheres, it is refracted and reflected in many different colours, so to speak. This gives the opal that beauty.
In comparison, glass is generally always transparent or translucent, this is a material that does not give colour at the touch of colour. This does not mean that glass cannot have colour, you can certainly add it by adding dyes during the melting process. However, this will never give the effect you will get with opal.
Water content and stability
In addition, an opal will always have a variable water content, which will be between 3% and 21%. The water is a crucial part of the opal structure, as it is incredibly detrimental for the opal to run out of water, this is because the opal may crack. In the worst case, the opal will even lose its play of colours. This makes opal a lot more sensitive than glass from the outset. This is because glass does not contain water and is also a lot more stable.
Glass is again a lot more robust and thus also less sensitive to some environmental influences such as dehydration. Yet glass can also break when subjected to strong impacts or extreme temperature changes. Still want to compare it with opal? Then we can say that glass is a whole lot more durable.
Use and applications
Glass is also a whole lot more versatile in terms of application and material. Just think what we all use it for, from windows to drinking glasses to even works of art. Glass really is a perfect material for practical and also aesthetic purposes. This is because it is easy to shape and is also generally transparent.
Opals, on the other hand, are more likely to be found in jewellery and also decoration. This is purely because of the beauty and also the colours of opals. For example, an opal would again be far too soft for everyday use, such as a window or drinking glass. Instead, these gemstones have been appreciated for centuries in different cultures as what it is, a precious stone.
Why is opal compared to glass?
The reason we compare opal to glass is because of the amorphous structure they share. Consequently, this is what they both are and they also both contain silica as their primary constituent. This absolutely does not mean that they are also the same material or were created or created in the same way, absolutely not. Glass is really purely "man made" and can only be made by melting and cooling. The other and in this case the opal was created by an entirely natural process. In this process, the silica gel has had a long time of deposition in the earth's crust. The reason why opal is often compared to glass has to do with their shared amorphous structure. Both opal and glass are amorphous and contain silica as their primary constituent. However, this does not mean that opal and glass are the same or created in the same way. Glass is a man-made material formed by melting and cooling, while opal is a naturally formed gemstone created by a long process of depositing silica gel in the earth's crust.
Another reason why the two are so hugely confused is because of a material called opal glass. This is a type of glass that you obtain by adding chemicals to molten glass. This gives the glass a milky and also opalescent appearance. So it basically resembles opal in appearance, yet it is nothing more than decorative glass. This glass is incredibly commonly used in lighting fixtures, decorative objects and also stained glass windows. The name can certainly lead to confusion. Nevertheless, it is important to remember that opal glass is not real opal and therefore does not have similar optical properties.
The history behind opal and glass
We have a rich history as far as glass and opal are concerned. They are also both valued for their beauties. Glass, for instance, is said to date back to ancient Egypt and Mesopotamia, here they would be used for decorative and especially practical purposes. Opal, in contrast, could already be found at the time of the ancient Romans. Here it was already valued for its value and symbolised purity and hope. This is why the Romans called opals opalus, which meant precious stone to them. Throughout the centuries, opals remained a valuable gemstone in different cultures.
Conclusion
We at Megalodontand.nl understand better than anyone how opal and glass can be similar. This, as we have already pointed out, is due to their amorphous structure and also the fact that they are both composed of silica to a very large extent. Yet they are two different materials. Glass is man-made while opal is purely natural. Glass was additionally used for decorative and functional purposes, while opal was known as a natural gemstone because of its beautiful colours.