Ouro Preto is a town of 70,000 inhabitants,
about 100 kilometres from Minas Gerais State’s capital, Belo Horizonte and is
world-famous for its colonial architecture and the works of sacred art by
Aleijadinho, whose real name was Antônio Francisco Lisboa (1730-1814)
considered by many as the greatest name of the American Baroque. His nickname means deformed, as he was a sculptor
that had to have chisels tied to the stumps of his hands so he could work.
When I told a Scottish friend of mine that I
would be spending a few days in Ouro Preto, he made me a rather curious
request: to buy him a flexible rock that I had never heard of. In fact, I
doubted its very existence. However, I
found references to it on the Internet,
and in Ouro Preto!
Even so, I remained unbelieving, incapable of
imagining how it would look like.
It seems to be an unfamiliar rock, for most
people questioned in Ouro Preto had never even heard of it. My friend had the
same difficulty when he was there years ago. He knew more about the flexible
rock than most locals. It was even suggested to me that it might be soapstone, so
well-known in Minas Gerais State thanks to Aleijandinho’s works of art with
that material, but I was sure its consistency would not make it flexible.
I hunted for information in the historical
centre of the old capital of Minas Gerais. At a jeweller’s, the manager told me
it was a very rare rock indeed, but could not tell me where to find it. I
insisted on my search when visiting a market for
articles made from soapstone. At one of the stalls,
it was suggested that I look for a dealer who sold stones of various types and
who also had a stall in one corner of the marketplace. The man knew about
flexible rock and affirmed that it was rare and the only place we could
possibly see it was at the Ouro Preto Mineralogy Museum, a few blocks away.
On entering the museum, my first thought was
regarding the flexible rock. And, lo and behold, there it was in a glass frame
with a wooden base and supports to hold it upright inside the glass. Its
identification was written at the bottom: flexible quartzite. Seeing is believing!
Quartzite is a metamorphic formed rock. The term itacolumite was first used for a Brazilian
quartzite thought to be a new type of
rock in 1822. Temperature
and pressure are factors that influence in its formation, resulting in
quartz-rich sandstone. Such conditions fuse the quartz grains
together forming a dense and hard rock. Its various colours depend on the impurities found in the rock
itself. Its main use is in pavements, ornamentation in buildings and swimming
pools and for building foundations due to its high resistance.
Flexible quartzitic rocks are found not only in
Brazil. It seems that the flexibility of the
rock is the result of well-interlocked junctions of the quartz grains that are
separated by uniformly-narrow inter-granular void spaces supposedly caused by
chemical dissolution of grain boundaries of quartz. According to modern analytical methods, the flexibility has been shown to be due to its porosity
that permits an interstitial movement where the interlocked grains are held
together in spite of their displacement. These factors can cause low
cementation of the crystals, making that part of the rock flexible.
There were samples for sale. I have my doubts
as to the rarity of flexible rock, as there were various samples to choose
from. Flexible quartzite resembles
sandstone and is quite hard just like other rocks. I examined and took a slab
of rock measuring sort of 40 x 20 cm, and cut to a thickness of about one
centimetre. It has to be lifted upright just as you do with a sheet of glass or
it will break in two. In this position you can admire its flexibility in all
its splendour, moving like a jelly. It is hard to believe, but the darn rock is
really flexible!
Having found the rock was quite a victory.
Returning home I sent an E-mail to my Scottish friend. He found it rather
strange that I had difficulty in finding the quartzite,
as he had seen it at the Mineralogy Museum. He only did not tell me that
before, because I had not asked him! When he was in Ouro Preto he had not been
able to buy a sample.
It was fine not to know where to find the
quartzite. It just made the adventure of discovery more interesting. The fact
that it is not well known makes me believe that it is hardly looked for,
forcing people that have heard of its non-legendary existence to the conclusion
that it is a very rare rock indeed.
It was necessary for a foreigner visiting
Brazil, coming from faraway Scotland, to tell us about the existence of this
interesting rock. The sample was adequately conditioned so it would not break
and was given to him as a memento in having given me the pleasure of
discovering another mystery of our country.
Three or four years later, I made contact
with the Mineralogy Museum to order slabs for my sons and myself. They were
conditioned in a heavy wooden box and sent over by post.
References
— Oliveira, Flávio Roberto
de – degree in Geography - Federal Institute of Minas Gerais (Ouro Preto
campus), 2015
— Wikipedia
(Internet)
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