1 – Amethyst
This gem is greatly appreciated for its beautiful purple color. The amethyst is a variety of transparent quartz to semitransparent. It is found in cavities of volcanic rocks and in pegmatites, another type of igneous rock. It is widely used as a gem and in ornamental objects. Its crystals can reach large dimensions, and one is in the British Museum, a crystal of about 250 kg.
In the private collection of Dom Pedro II, ex-emperor of Brazil, there was a crystal of 80×30 cm, which comes from Rio Grande do Sul. In this state, it was discovered a geode (cavity lined internally of crystals) measuring 10 x 5 x 3 m with 35 tons. The color of the amethyst that stays long exposed to the sun can weaken. This happens in Brazil mainly with the amethysts coming from Pará. The lost color can be recovered with the use of x-rays.
Heated at approximately 475° C, the amethyst can turn into citrus, a yellow, orange or exceptionally red quartz. Rio Grande do Sul produces a lot of citrus from this process. It should be remembered, however, that not all citrus is obtained from the amethyst, as there is natural citrus.
Some rare amethysts when heated become yellow-green and are named brasilinite. The largest amethyst producer in the world is Brazil followed by Bahia. Other producers are Russia, Sri Lanka, India, Madagascar USA and Mexico.
2 – Grenade
Granada is not the name of a gem, but a group of them. They usually appear in nature in the form of beautiful granular crystals in red, yellow, brown, black colors and more rarely green or colorless. They are transparent to semi-transparent. The main producers are Czech Republic, South Africa, Russia, Australia, Sri Lanka, Austria, Hungary, Germany, India, Madagascar and USA.
3 – Lapis Lazuli
Lapis lazuli is a gem that, unlike the vast majority of others, is not a mineral but a rock. In fact, it is a rock composed mainly of lazurite and calcite with hauynite, pyrite, sodalite and other minerals. Pyrite forms yellow dots and is a good way to identify true lapis lazuli. It has a dark blue color and can be opaque to semi-translucent. It is used as ornamental objects.
The best quality lapis lazuli is the one produced in Afghanistan. There is also production in Chile, Iran, Russia and USA. Lapis lazuli has been synthesized since 1976 with great perfection, and it can be extremely difficult to distinguish it from the natural one. It is considered the national stone of Chile, where it is mined in Cerro Azul, in the north of the country.
4 – Emerald
Emerald is also one of the most used gemstones and women love the jewelry items made of emerald. For the best emerald stud earrings.