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Minerals and Gemstones

There are more that 4000 mineral types known in the nature. What do we know about them?

Structure

aragonite
halit

The crystals' structure is a logical arrangement of atoms, ions or molecules in the space and is formed under certain physical and chemical conditions, taking the form of Polyhedrons. For example the crystal structure of halit (which is our well known in the kitchen salt) is cubic - the molecules form a single cubic cell which is surrounded of many other single cells and so finally the big crystal has a cubic form itself!


This specific structure creates the amazing world of the crystals determining every single property they have. Thus the carbon forms cubic crystals of diamond or hexagon lattice of graphite.

That is what make crystals amazing - some for its shape, others - for its dimensions, third - with unusual colours, but certainly – they all are extremely beautiful.

How do we use them?

The minerals have many different purposes. Many for example are not particularly impressive in appearance but are used in industry or have a medical function. In general almost all minerals used in the trade are divided for the convenience of two major groups:
- Simple, but useful in industry;
- Precious and semiprecious stones of lower quality and therefore not suitable for jewellery.

For example diamond and corundum (which most beautiful and valuable varieties are gemstones ruby and sapphire) are the hardest natural substances and the most beautiful examples of these are processed by highly skilled craftsmen for rings, brooches and other items for decoration. Even if they do not have enough beautiful appearance for use in jewellery they have worth as abrasives in the industry because they are very hard.

Ultimately the most important factor, which depends on the analysis of the use of each precious stone is the price that he was able to achieve on the market. The minerals classified to the group of gemstones, are sufficiently rare and beautiful. The more rare is a gemstone the more expensive it is.

Unit mass of precious stones

Unit weight of gemstones is carat, standard unit in the world: 1 carat = 0.2 g; internationally accepted measure of gems is the metric carat, weighing 200 milligrams.

Some classification

Gem stones have the following classification: precious, semiprecious and ornamental gem stones. The transparency of the structure is typical for the precious and semiprecious stones. The ornamental stones are opaque or have a barely noticeable tint. Their price can greatly fluctuate and the price of some rare ornamental stones can be close to the price of precious and semiprecious.

Rarely occurring in nature gemstones are diamond, sapphire, ruby, emerald. These stones should be in gold plate.
The most common semi-precious stones are alexandrite, tourmaline, topaz, amber, opal, garnet, amethyst, aquamarine, turquoise. They can be in gold plate, but they fit perfectly and silver.

Stones belonging to ornamental are onyx, malachite, agate, lazurite, jade, adventurers, obsidian, rhodonite, tiger's eye, chalcedony, jasper. They can be used for large-scale artistic decorations or household items, gifts, candle holders, jewellery boxes, figurines and more.

More about minerals and gemstones from National Geographic


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