Mineral, crystal, gem. Introduction to terminology.

Each piece of jewellery can be divided into three important elements. Two of them are materials: metal and gems. The third is the skill of the jeweller, who combined the materials into a beautiful piece.

In this article, we would like to delve into what gems, minerals, and crystals are. Are these words synonyms, and how to work with them correctly?

Mineral

Let's start with a fundamental concept - a mineral. According to the definition, a mineral is a chemical compound or chemical element with a crystalline structure and a well-defined chemical composition, which was formed as a result of geological processes.

A well-known mineral is a quartz. It has a certain formula (SiO2), defined crystal structure and was formed as a result of magmatic and metamorphic processes.

Minerals that are commonly used in jewellery, such as diamond, sapphire, ruby, emerald, topaz, tourmaline, aquamarine, and chrysoberyl (alexandrite) also have their own specific chemical formula and ordered structure. Usually, they form crystals of amazing shape. Chrysoberyl is sometimes found in crystal twins in the form of a snowflake or heart.

Kyanite mineral in quartz matrix.

Photo by O. Rybnikova

Crystal

Quartz is also a good example to illustrate what a crystal is. We all know what a quartz crystal looks like - it is a hexagonal prism, with a pyramid on the top. The crystal can have a very different appearance. An example of crystal is a diamond octahedron, a garnet dodecahedron, an emerald prism, malachite needles and thin mica plates. The shape of a crystal reflects its internal structure of ordered atoms.

Minerals can be mined in the form of a crystal, and can also occur in massive form, where single crystals are indistinguishable. For example, agate is a cryptocrystalline variety of quartz and the crystals cannot be seen with the naked eye.

To summarize: every natural crystal is a mineral, but not every mineral can be in a well-defined crystalline form.

Photo by O. Rybnikova

Gemstone

According to the International Mineralogical Association (IMA), 5, 780 minerals are currently known. Not all of them can be used for jewellery purposes, as some minerals can be only a few nanometers in size. Minerals can be too soft, uncuttable, very rare, or simply unattractive. Therefore, in the jewellery industry, we often hear such a word as a gemstone.

A gemstone also has its own definition. In order for a mineral to have the honour of becoming a gemstone, it must fulfil several criteria:

1. To be rare
2. Durable (resistant to environmental conditions)
3. Aesthetically attractive.

The number of gems that exists is the subject of much debate. Someone remains an adherent of the old classification that there are four of them: diamond, emerald, blue sapphire, and ruby. Sometimes the list is supplemented with alexandrite. At the same time, the rest of the minerals (topazes, tourmalines, beryls) fall into the category of semi-precious ones. This classification is considered a little outdated since the price of some semi-precious minerals can sometimes even exceed the price of a diamond.

Nowadays it is widely accepted not to divide stones into precious and semi-precious categories. That is why the term gemstone (gem) is used. The Gemological Institute of America (GIA) lists 29 gemstones in its encyclopedia. In turn, the International Gem Society (IGS) lists 304 gems.

It is also worth mentioning that not only minerals are used in the jewellery industry. For example, amber, jet, pearls, coral and mother-of-pearl are materials of organic origin. While lapis lazuli, charoite, and tiger's eye are rocks (a natural association of one or more minerals). Opal is also an exception. From a scientific point of view, it is a mineraloid (a mineral without a defined crystalline structure).

In summary, a mineral is a more scientific definition, a crystal is a formation with distinct facets and edges, and a gem is any mineral, rock, or material of organic origin that is durable, rare, and aesthetically pleasing.

Various faceted gemstones. Photo by O. Rybnikova

Rybnikova Olena - gemmologist, MSc in Mineralogy, Geochemistry and Petrography. Taras Shevchenko National University of Kyiv alumnus. Applied Jewelry Professional certified by Gemological Institute of America. Now she is doing PhD in Europe and is writing a dissertation on the beryllium minerals topic. Actively popularizes gemstones and gemmology.