NATURAL STONES: LEARN WHAT ARE THE TYPES OF GRANITE AND QUARTZITE

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For millennia, planet Earth has provided mankind with stones for the most diverse uses.
At first, these stones were used as tools, shelter, and as a backdrop for telling their stories and recording their arts.

More recently, but still, millenary, man found in the natural stone the key elements to carry on with recording his history, however, in a more grandiose and daring way, in the construction of his empires.

In the meantime, many incredible projects were created, man cut, sawed, moved, and built the unimaginable, from pyramids to temples for their gods and palaces for their nobles.

Masterpieces, relics of our history were carved, sanded, and polished by hand almost as if by a miracle for their time. Stone as a covering, extracted and processed for use in buildings, is something that comes from ancient times, with remarkable appearances in palaces such as those in Europe.

At first on the floors and walls, the stones quickly found space on tables, kitchen countertops, bathrooms, and wherever else creativity and necessity allowed their use.

From then on, the use itself showed to the professionals who chose these stones — already as covering materials for their projects — that some of them were better suited than others for each type of application.

Stones that wore out mechanically, stones that were more or less susceptible to scratches, stains, and other problems that often led their choices to suffer from irreversible pathologies, severely damaging projects that were often so desired.

Thus, architecture and design professionals, in addition to the consumers for whom the projects are carried out, began to demand from stone suppliers more information that would guarantee their choices, when the question was stones for coverings, also known as ornamental stones.

Thus, considering this scope, a strong process of study, technological characterization, search for new stones, new mining systems, and mining of these stones in nature began, so that the stone industry became able to provide this service and had products suited to each specific demand for each type of project.
All of that, in a way that would guarantee to projects, from small residences to large corporate buildings, or important public facilities, everything it proposes to give: beauty, longevity, and timelessness, depending on the type of stone or rock chosen for each project.
Within this scenario, the famous marbles did not lose their space but began to share it mainly with granites when extraction and processing technologies only allowed processing up to that point of stones’ hardness.
In summary, in the last two decades, especially here in Brazil, with the development, evolution, and transfer of technology of diamond wires from the quarries to the factories, quartzites came up.
Stones of very high hardness, extremely resistant, and with unique beauty, in addition to being timeless, quickly became a trend and, today, it can be that they are a reality that has come to stay in the segment of natural stones for coverings.

WHAT ARE GRANITES?

Conceptually, granites are rocks composed essentially of quartz and feldspar and to which, in much smaller amounts, mafic minerals such as biotite or felsics such as muscovite are often associated.

A slow cooling process forms them, giving quartz and feldspar crystals time to grow larger. Thus, you can see colors in it that correspond to the shades of feldspars and micas, grains of different types of granite colors, with granulometry that can go from a few millimeters to centimeters in diameter.

In the White Alpha granite, for example, one can see gray dots, which are quartz crystals, the white area, which is feldspar, albite/plagioclase in this case, and the black dots, which are biotites.

Quality granites are characterized by high amounts of quartz, above 25% — Alpha has got between 30% and 35% — low absorption and high wear resistance. Ceará granites, in this case, stand out in the world for technically meeting rigorous application demands.

However, ornamental and covering stones, commercially called granites, are not always stones of this petrographic group.

To exemplify, we can mention materials such as Matrix Motion, which is treated as granite, but in reality, it is schist, the Imperial Brown, which is a syenite, the Ceará Black, that is a ganobrito, and the stones of the Marinaces family, which are actually metaconglomerates.

High-quality granites, due to their good technical performance, are widely used on floors of high-traffic areas, such as airports, shopping malls, and ventilated facades, among other applications.

Because of this type of use, granites, when polished, lose a lot of their space in smaller interior works, such as residential ones, precisely because of their pigmentation. Because they are so much used in areas of collective use such as shopping malls, they started to be seen as “a common covering”.

Seeking to become a trend again, the stone industry had to reinvent itself and launch different and innovative surface treatments, which raise the level of granite, changing its “cliché” status.

Treatments such as Matte and Velvet make granite stones special and unique and, moreover, make any indoor or outdoor area contemporary, modern and timeless.

This can be seen in works around the world, such as the Louvre Museum in Abu Dhabi and The Shard in London, which internally used materials with opaque and texturized treatments.

WHAT ARE QUARTZITES?

Quartzite is a metamorphic stone basically made up of mineral quartz, which begins its life in the form of grains and sand such as dunes and river beds and, over time, is compressed to form sandstones.

However, if buried deeper under layers of rocks and associated with an increase in temperature and pressure, they lose their original shape and fuse with their neighbors, forming a dense and durable rock.

Normally, these stones have light tones and they can assume other colors due to additional minerals carried by the groundwater, transferring tones such as green, blue, and red.
Among the stones for coverings, the hardness of quartzites is the highest, because they have more than 75% of quartz in their constitution, reaching in some cases more than 90%, such as Perla Santana, which has 94% in its composition.

https://www.dropbox.com/s/o3wmmz3g9llsgsd/Perla%20Santana%20%40s tudiocolnaghi%20CH%20Ph%40donadussi%20d.jpg?dl=0 => Perla Santana countertop.

This makes quartzites harder than glass and knife blades, which can easily be seen when trying to scratch the stone with one of these elements.

In addition, they are materials with very low porosity and absorption when they are “crystalline”, which indicates a very high degree of metamorphism, that is, when the sandstone — protolith, the rock that preceded the metamorphism and that generated the quartzite — suffered the highest temperatures and compressions, reaching 800ºC.

Not to mention the crystals that, in the beginning, were sand and ended up melting, forming this super stone, like Perla Santana, a true quartzite.

Another element that evidences a quartzite is the non-reaction of the stone to the presence of acids.

In contrast, marbles, for example, no matter the type, react to these elements. It is worth remembering that almost everything that is manipulated in a kitchen, mainly, has acidic substances in its composition, like tomatoes, lemon, olive oil, and wines.

Attention to this point: there is in nature a group of stones that are the meta sandstones, which are nothing more than sandstones that have also undergone metamorphisms, however, of low degree and low intensity.

 

What evidences this is the low cohesion between the crystals, causing these stones to have from moderate to very high absorption.

They are stones that do not react to acids, they have high hardness, and they are formed from the same quartz as quartzites, however, their formation is “in the middle of the way”, the following images can illustrate this didactically.

Quartzites are the great revolution in the sector of stones for coverings, their appearance in nature dates back to 600 million years.

However, because of the high hardness and extremely fragile structure when in nature — because of fractures suffered in its formation process that goes to extreme conditions — it took a revolution in mining and industry so that stone could be mined and processed.

The origin of diamond wire, which began in Italy in the 1970s, arrived in Brazil in the 1990s, and entered industries at the end of the same period, reached its peak only in mid-2010 when quartzites could be extracted from nature and processed in the industry.

These are unique stones that add value to any project, as they have a classic beauty like that of the noblest marbles, with the maximum resistance that only they have in nature in quantities and conditions of use for coverings.

With the emergence of the internet and the wide spread of information regarding the composition of synthetic materials, many companies began to appropriate themselves to the word “quartz”, transforming it into a value for their products.
However, a covering having quartz in its composition, or even a stone, does not make it a quartzite.
Today, there is a great amount of information about sintered synthetic materials, ultra-compacted porcelain tiles with high resistance, and the convenience of using a standardized material, since natural stones have nuances “produced by nature”.
The fact is that none of them have the weight of a history that was formed 600 million years ago, going through the most extreme weather that something can go through being “forged” inside the Earth and maintaining the unique characteristics that all of this produces, generating a unique and timeless beauty.

3 MAIN DIFFERENCES BETWEEN GRANITE AND QUARTZITE

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