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Learn more about gemstones and the difference between Precious and Semi-precious stones.

 A gem is any natural material suitable for use as an ornament. It has three characteristics, it should be beautiful, durable and rare.  The traditional classification, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious. In modern use the precious stones are Diamond, Ruby, Sapphire and Emerald, with all other natural gemstones being considered semi-precious.


Precious stones versus Semi-precious stones

Diamond, Ruby, Emerald and Sapphire


But is it always the case that the above stones are more valuable than their semi-precious counterparts? Well not exactly, quality is also very important. Inclusions within the stones and their clarity can affect a stones value tremendously, with a poor-quality Emerald likely to be worth less than a top-quality green Garnet, for example, despite its loftier title. As a rule of thumb, the big four are likely the most valuable stones you will find, and you can then use the “four Cs” - colour, cut, clarity and carats - to separate them after that.

At Mosaico, the focus is on semi-precious stones only, and there are two main reasons for that.

The first is cost. Our pieces are designed to be affordable luxury, a style statement that you love to wear but that doesn’t cost the Earth. The second reason is the variety of colours and markings! Although the sparkle and value of precious stones are beautiful, the stunning markings, colours, shape and variety you can find on semi-precious gemstones are pretty special and more unusual. For example, the stunning markings of a banded Agate or Ocean Jasper are just undeniably unique and fabulous. But of course, that is our opinion.


Ocean Jasper necklace

Esther: Ocean Jasper necklace


How to classify semi-precious stones


We have to start with the umbrella term “Quartz”. This is one of the most common minerals on Earth, and also one of the most varied. They are all made of silica that forms crystalline structures. There are two main types: macrocrystaline with crystals that can be seen by the eye, and microcrystalline, where they cannot. Microcrystalline Quartz stones are usually called Chalcedony. These two names together describe a huge number of semi-precious gemstones.



Types of Macrocrystalline Quartz crystal

Types of Chalcedony





Smoky quartz


Rose quartz





Tiger’s Eye

 * amongst others


These stones display a magnificent range of colours and patterns. The fact that a deep red orange Agate gemstone is made of similar material to a gorgeous purple glinting Amethyst crystal is just down to the chemistry inside each stone when they were formed.

Amethyst long necklace

Aurora: Amethyst long necklace


Beyond Quartz

So what is left? We’ve picked 6 more of our favourites and explain their origins.

Lapis Lazuli

This is the first non-crystal on our list, as Lapis is actually a deep blue metamorphic rock. It can contain as many as 15 different minerals, all squeezed together in the Earth’s crust under huge pressures. The deep blue colour is caused by Sulphur, whilst the characteristic yellow or white patterns are caused by the presence of Pyrite and Calcite respectively.

Lapis Lazuli bracelet
Bluebell: Lapis Lazuli bracelet



We’ve gone into great detail about Pearls and Mother of Pearl in a previous blog post (link) if you want to know more. This gorgeous stone is formed naturally inside the shells of some molluscs underwater and has a gorgeous lustrous glow. This is not a ‘stone’ in the tradition sense but is categorised as a gemstone due to its rarity, durability, and beauty. Mother of Pearl earrings

Arabella: Mother of Pearl chandelier earrings



Topaz is one of the hardest naturally occurring minerals, making it ideal for everyday jewellery. This hardness is one of the key characteristics that set it apart from categories of Quartz. It comes in a variety of colours but most common are yellows, oranges or reds. The popular variety of blue topaz is stunning but very rare in nature and is usually formed by heat treating the clear variety, altering its chemistry. Topaz hoop earrings

Amelie: Blue Topaz earrings



Amazonite is a deep green variety of the mineral Microcline. As the name suggests it is found widely in Brazil. Although a silicate like the Quartz family, its crystal structure is different due to their formation within slowly cooled igneous rocks.

Amazonite long earrings 
Mary Alice: Russian Amazonite earrings



The spinel has a deep red colour and is chemically similar to the Ruby.  Ruby is a crystalline form of aluminium oxide but in Spinel, magnesium atoms as also present.  A pure Spinel stone would be colourless, but the majority found in nature are red or pink, due to the presence of iron.



Finally, on this gemstone list, the Turquoise stone. This blue-green mineral is made from copper and aluminium phosphate. The name derives from the old French word for “Turkish”, as that country was the gateway for the mineral to first enter Europe. It is said to be the most valuable non-transparent mineral in the jewellery trade, but it is important to be careful, as the stone is sensitive to sunlight, water and soap.



Gemstone jewellery pieces are beautiful, colourful and fun! Before you purchase them, our advice is to compare the price asked with the grade and quality of the materials of the jewellery. Natural gemstones such as Lapis Lazuli are also graded, and they vary from ‘B’ to ‘AAA’ grade, the latter being the best and most expensive one. Anything above ‘A’ is considered of high quality. Other questions to ask are:

  • Are they sustainably sourced?
  • Are these pieces handmade? If yes, by who? Please note that there are many retailers claiming their pieces are “handcrafted” which can turn out to mean that they are mass produced in Hong Kong or China. If you are looking for uniqueness, these might not be for you.
  • What extra materials are being used to finish the design. If you are being charged well for a particular piece, ensure any metal findings are made of solid silver (925 Sterling Silver), Gold-filled or Gold Vermeil – as they are the most durable. These are the best materials for affordable luxury you can find. If you decide to go for solid Gold then you will certainly feel it in the price.

Our pieces are designed and handmade in the UK (by us!) with sustainably sourced high-grade materials. All stones are grade A and above and the findings are solid silver, Gold Vermeil or Gold filled. If you are looking for affordable, luxurious and truly unique semi-precious gemstone jewellery, have a look at our designs.