READER QUESTION Guilherme Cardoso Lima, Sao Paulo, SP
ILLUSTRATES Marcos Penna
EDITION Bruno Lazaretti
The same geological processes that create, shape, and reshape the Earth also generate temperature and pressure situations that combine elements into stones precious. The exception is organic gems, such as pearl and coral, which are made by living things but classified as minerals.
There are three types of rock in the Earth’s crust: igneous, metamorphic and sedimentary, which can be understood as different phases of a cycle, as they transform into each other over time. Igneous rocks form from magma or lava. Metamorphic rocks are formed from rocks that undergo heat and pressure without melting again. The sedimentary ones arise from rock residues or organic matter dissolved in water. It is in the midst of all this swirl of magma, sediments and rocks that the stones precious They emerge.
Not everything that glitters is gold
Where and how some of the most famous gemstones are formed
– (Marcus Penna/Strange World)
1.Diamond
Made only of carbon, diamond is one of the few stones precious that do not usually form in the Earth’s crust, but in the mantle, an underground ocean of magma. The pressure and temperature of the mantle, capable of liquefying rocks, also compresses and fuses carbon in the form of diamonds, which are carried to the surface by magma, mixed with igneous rocks.
- In rare cases, the pressure that forms metamorphic rocks in the Earth’s crust also forms diamonds.
2.Peridot
It is another of the rare gems that form in the Earth’s mantle rather than the crust. Peridot is a variant of the mineral olivine, a mixture of magnesium, iron, and silica (silicon and oxygen) combined under the heat and pressure of mantle magma. When these elements combine in the right proportion, richer in magnesium, peridot forms. With luck, it rises to the surface next to igneous rocks
– (Marcus Penna/Strange World)
3.Jade
What we call “jade” are actually two different minerals, jadeite and nephrite. They form in the same process that forms metamorphic rocks, when temperature and pressure deep in the crust recombine elements from stonesbut without melting them (which would turn them into magma)
4.Emerald
Formed by the combination of the elements beryllium, aluminum, silicon and oxygen in an aqueous solution, emeralds usually occur in veins of hot water (hydrothermal) derived from magma deep in the earth’s crust. When this aqueous solution of these four elements cools, the emerald solidifies.
5.Ruby and Sapphire
When magma containing aluminum and chromium encounters air pockets in the Earth’s crust that contain oxygen, these three elements combine to form rubies. Chromium, a rare element, is what gives a ruby its red color. If he is not present in the game, the gem formed is the sapphire, which is usually blue.
6.Quartz
It is formed by the evaporation of an aqueous solution containing silicon atoms, which occurs both in surface water veins in the Earth’s crust and in hydrothermal veins. With the presence of certain impurities (such as iron) during its formation, quartz can turn violet in color, also known as amethyst
7.Turquoise
Similar to emerald, turquoise comes from the combination of elements (phosphorus, copper and aluminum) in an aqueous solution. The difference is that this solution does not derive from magma in the mantle, but from the infiltration of surface water into the Earth’s crust. When the seepage gets deep enough for the heat to evaporate the water, turquoise forms.
How much do you want to pay?
The more “unique” the combination of impurities and deformities, the more valuable the stone. Check out some of the most expensive ones:
1. Pink Star Diamond
It is a large specimen (11.92 g) of an expensive and rare type of diamond, the pink diamond. No one knows for sure how they get that color, but most likely the presence of structural anomalies. In 2013, it was auctioned for $83 million.
2. Painite
This type of crystal, resulting from the evaporation of an aqueous solution in surface veins, was discovered in 1950. Its rarity is a result of the amount of elements needed to form it: calcium, zirconium, boron, aluminum, oxygen and iron. Its price can reach US$ 60,000 per carat
3. Musgravite
An ore formed from evaporating surface water or from hydrothermal vents composed of magnesium, beryllium, aluminum, iron, and oxygen. The rarity comes not only from beryllium, a scarce element, but also from the difficulty of finding the mineral in the form of translucent crystals. It costs US$ 35,000 per carat
4. Jadeite
The rarest jade variant is created in stones metamorphic substances that combine sodium, aluminum, iron, silicon and oxygen. It’s hard to find because the pressure needed to produce it in metamorphic rocks is quite high. Worth $20,000 a carat
5. Alexandrite
It is a rare species of the already scarce beryllium crystal, like musgravite. Alexandrite is especially desirable because its molecular structure (which is largely determined at random) causes its color to change with light. Costs $12,000 a carat
SOURCES Petrobras, Só Biologia, Discovery Channel, Geology, Berkeley It is gemstones; book gems and stones preciousby Ronald Louis Bonewitz, and Guinness Book