Mineralogy and its specimens

Quartz is one of the most common
and widespread minerals in the earth's crust. It is a fundamental element of
all rock types. It has a glassy luster and can crystallize in the rhombohedral
system with crystals in the form of a prism or pyramid. Hardness is another
quality of this mineral, rated 7 on the Mohs scale, which goes from 0 to 10. 

Another characteristic of quartz is its piezoelectricity, which is the property of generating electrical voltage as a response to mechanical pressure. For these reasons, quartz has great application in industry, from the manufacture of electronic circuits, computers and fiber optics to the production of glass and ceramics.

CITRINE

This is a variety of quartz with a yellowish color due to the presence of trivalent iron. Most of the Citrine commercialized is obtained by heating amethyst. Brazil is the world's largest producer of this mineral.

AGATE

Here we have a beautiful and important variety of chalcedony. It is formed mainly in the cavities of volcanic rocks and usually has its colors distributed in parallel or concentric bands.

It has been used as jewelry for more than 3 thousand years. Brazil is the world's largest producer of Agate.

GEODE

Spherical cavity of quartz crystals very common in basaltic rocks.

This cavity is formed by gas bubbles that can later be filled by other minerals in hydrothermal solutions, giving rise to crystals inside this hollow chamber.

SLATE

Metamorphic rocks are those that arise from the transformation of preexisting rocks when submitted to a change in pressure and temperature.

They are widely used in civil construction for flooring, walls, and the manufacture of tables and countertops.

Slate is a metamorphic rock originated from the transformation of clay, which was hardened in thin layers, presenting a gray color and fine granulation.

Schist

Generic name to designate several types of metamorphic rocks that present themselves in the structure of very thin layers.

Husk´s shales have shown potential for the production of the gas and oil that are incremented in the oil production chain. Brazil has the world's second largest reserves, second only to the United States.

Metamorphic rock with
a grayish color and rich in feldspars and quartz. They are basically
differentiated by their structures. Gneisses commonly present lighter bands,
composed of quartz and feldspar, and darker bands, formed especially by
minerals that have iron in their composition.

This is what
sedimentary rock formed in glacial lakes is called. It is arranged in layers
that define the seasons of the year and prove some climatic and geological
variations on the planet. 

The light layer indicates the summer season when sand and silt, coarser particles, precipitate at the bottom of the lake. The dark layer is formed in winter, when the lake freezes and only fine sediments like clay can precipitate.

Stalactite

Caves are natural cavities in the lithosphere that allow access to humans

They are surely one of the most spectacular landscapes on Earth.

On their roofs, water enriched with calcium carbonate drips down, seeping from the surface into the cave and giving rise to stalactites.

FOSSIL

Fossils are the remains or traces of animals and plants that were preserved in rocks.

They are true records of the ancient life of our planet.

From the study of fossils, it was possible to prove several natural events, such as the evolution of species and the movement of continents. Here we have a beautiful fossil of a fish.

Amorphous
mineralolide (without defined form) of yellowish color. It is a fossil resin,
formed by various substances soluble in chlorine, ether and alcohol. It can
contain air bubbles, plant remains, and even insects in its internal structure. 

It is used as a gemstone in the jewelry industry. It has never been found in Brazil. The world's largest producers are Germany and Russia.

Colorless mineral, commonly
white, with vitreous luster and low hardness (3.0), being easily scratched with
a razor. It presents perfect cleavage, it will always break into equal pieces,
even at the microscopic level we will see that its shape is maintained. Calcite
is a carbonate found throughout the world. Very soluble, it is used to make
cement, mortar, and paint.

A curiosity about this mineral is that even if you hit it with a hammer on it, it will always break in this shape, as if it had been cut on a knife.

Even if you get the size of sand and look at it with a magnifying glass or microscope, you can see that the shape of it always remains the same.

One of the most
fragile minerals in nature, hardness 2 on the mohs scale. It has a white or
colorless color. Its luster is silky, glassy, or pearly. Gypsum is very present
in meteorites that reach the Earth.

It is widely used in the manufacture of cement, plaster, chalk, glass, enamels, and sulfuric acid.

The largest producers are Great Britain, Egypt, and Mexico.

DOLOMITE

Very common mineral in the earth's crust, and also present in meteorites. Used as thermal insulator and ornamental stone.

It has a hardness of 3.5 to 4.5 mohs and forms rhombohedral crystals.

Its name comes from an homage to the French chemist Gratet de Dolomieu.

It has this name because it has
sodium in its chemical composition. Generally, its specimens have a beautiful
and distinctive blue color. It is widely used as a gemstone for the jewelry
industry or in ornamental articles. Brazil is the world's largest producer.

It is the famous
sodium chloride NaCl, also known as rock salt. A mineral of low hardness,
easily scratched with the fingernail, and that presents a cubic crystalline
habit, that is, its crystals have the shape of a cube. 

Since the early days, it has been used as a seasoning in human food to make chlorine and caustic soda.

Most common mineral of
the Mica group. Mica is the group of minerals that have a foliated crystalline
habit, that's right, its crystals are like leaves or scales, and the basal
cleavage, that is, the mineral always breaks into sheets. 

Very common in igneous and metamorphic rocks, Muscovite is widely used as a thermal insulator, since it has null heat conductivity.

It is also a mineral from the Mica group. Often confused with
Muscovite, it can be differentiated by its chemical composition, dark color and
greater flexibility.

This is the mineral
with the lowest hardness found in the lithosphere (1 mohs). It can crumble with
the simple touch and pressure of hands. It has a whitish color and pearly
luster. Very important for the cosmetics industry, because when used in powder
form it generates products to treat skin and, mainly, for baby care.

Talc is the main component of soapstone, a rock that, in Brazil, became famous for the sculptures by the artist Aleijadinho.

Here we have a sample
of Galena (dark part) associated with quartz (light part). The Galena mineral
is responsible for the production of lead, it is presented in cubic crystals
with a strong metallic luster that sometimes becomes matte due to oxidation.

If by medical necessity you have to have an X-ray, remember that the protective barrier is a lead plate. Ammunition and batteries, too, are made of lead.

This is Iron Oxide,
has a gray color, and produces a reddish trace, that is, if it is scratched
against a matte porcelain, it will leave a reddish powder. It is the mineral
that gives rise to iron, elemental to the development of modern industry.

The importance of iron, the raw material for steel, can be seen in all aspects of modern life: tools, machinery, building material, household appliances, transportation, etc.

Pyrite or iron sulfide is the most abundant of all the
sulfides. It is also known as "fool's gold", because in ancient
trading, it could become oxidized with a color similar to gold, only with low
economic value. It crystallizes into magnificent brass-yellow cubes of medium
hardness (6 - 6.5 mohs). It is present in fossils and meteorites. The world's
largest producers are: France, Italy and Germany.

It is also known as "fool's gold", because in ancient trade, pyrite, which when oxidized turns a yellowish color, resembles gold, only with low economic value.

Black or dark brown iron hydroxide. It is used to obtain iron
for the steel metallurgical industry. Its name is a homage to the German poet
Goethe.

High hardness aluminum oxide (9 mohs) widely used as
abrasive.  It has a vitreous to
adamantine luster and variable colors. It is used as a gemstone in the jewelry
industry under the name of ruby, when it has a red color, generated by
impurities such as chromium and iron, and sapphire, when it has a blue color,
generated by impurities such as iron and titanium.

Corundum was also widely used for its high hardness as an abrasive.

Like silver and
sulfur, it is a native element that occurs without association with other
chemical elements in nature. It is the most malleable and ductile of the
minerals. With 1 gram of gold, you can get up to 2,000 meters of wire just
0.0001 millimeters thick, and it is a very good conductor of heat and
electricity. 

Gold has historically been used for producing coins, making jewelry, and more recently in the electronics industry. In the picture you can see the gold grains that are present in the rock.

FLUORITE


A mineral with worldwide extension, it presents perfect cleavage, that is, when subjected to mechanical force it always breaks into cubic faces. Some fluorite also has the fluorescence phenomenon. Widely used in the chemical industry (manufacture of fluorine), manufacture of glass, enamels, and optical instruments.

MAGNESITE


Magnesium carbonate, formed by the alteration of dolomites and limestones in magmatic solution. Used in refractory ceramics, electrical insulators and to obtain magnesium.