(or: "Amethyst mining in the Caxias do Sul city region, Rio Grande do Sul, Brazil)
A Geo-Report from Heinrich Frank
The first information
Some years ago a man came to the Geological Museum of CPRM, a geological survey company located in Porto Alegre, with a piece of apophyllite with a prismatic piramidal habit, difficult to find among the apophyllites in Rio Grande do Sul state. Asked by the curator of the museum, geologist Pércio de Moraes Branco, for the origin of that piece, the man only said that it came "from a quarry between the cities of Caxias do Sul and Canela".
Pércio knew my vivid interest in zeolites and passed me that information. In the first half of 2002 I have had the opportunity to travel through that region - between Caxias do Sul and Canela - and asked for quarrys. Talking to people who live there, it was easy to get a name connected to quarries and "garimpos" (= mines): Nelson Silvestre, living in the small town of Santa Lúcia do Piaí. I spoke with him on that occasion and we agreed to visit the garimpo, the amethyst mine, after the cold and rainy winter.
After october, really cold and rainy, at the beginning of november we phoned and I made the visit and so I have the pleasure to tell you this story.
THE IMMIGRANTS
At the beginning of the 20th century many immigrants came from Italy to Brazil. Among this people were a girl, 9 years old, and a boy from another family, called Silvestro with surname, also not older than 10 years. Living in the southest state of Brazil, Rio Grande do Sul, they grew up, got to know each other, married and lived in the locality of São Paulo, district of Santa Lúcia do Piaí of the county of Caxias do Sul, in the Rio Grande do Sul state. One of their sons, called Sebastião, bought a property in 1930 with 72 hectars between the towns of Santa Lúcia do Piaí and Vila Oliva. This is the place of our interest. Sebastião found there "an ocean" of araucaria trees, typical pine trees of southern Brazil. This dense araucaria forest extends till São Francisco de Paula city, 100 km to the east. Today very few of those trees remain - some here and some there, all of them protected. The wood of these trees built the houses and the fortunes of many people. Sebastião raised pork and grew wheat and corn.
THE TRIP
To go to that place, you take the road BR-116 up to the kilometer 147, just after the bridge over the Caí river, 200 meters before the toll. There begins a good non-paved road who enters the Caí valley upstream. You follow the road about 10 kilometers.
Valley of Caí river seen from the road BR-116
Big and scenic, Malakoff Mount rules the valley. People who travel from Nova Petróplis to Gramado city and don't visit this mountain don't know what they are missing.
Then you follow a road to the east, to Vila Oliva. 10 kilometers more and you reach the garimpo of the Silvestre family.
Still on the very good unpaved road to Vila Oliva, you see a great number of quartz crystals and geodes with agate on several roadcuts, where the crystals concentrate on the base of the organic soil due to intemperism processes. Beneath, there is a totally altered basaltic rock. Without any difficulty I collected quarz crystal groups 2 cm high, very clear and sometimes a little bit blue. Agate, dehidrated agate, chalcedony and quartz in strange forms, skeletal and ruiniform, can also be found there.
THE BEGINNING OF THE GARIMPO
The old Sebastião Silvestre (the name now ends with "e", not with "o" as original) was not specially interested in "the stones" - the amethysts. On one occasion, an older man from Caxias do Sul visited the Silvestres, picked up some amethysts from the soil and sold them in Soledade city, a big trading center for precious stones in the state of Rio Grande do Sul. In this way the collecting of the amethysts started with shovels and picks. The collected stones were put in a bag(!) and the Silvestres brought them by bus to Soledade city.
This happened 40 years ago. The mining evolved and Sebastião and his family, now with son Nelson Silvestre, searched for the amethysts, always with picks and shovels, when the work in agriculture, the most important work of the property, diminished. This way they worked with stones mostly in the winter.
But now it was not necessary to bring the stones to Soledade: the buyers came to the Silvestres, with cars like Chevette and Corcel, buying small quantities as 100 or 200 kilograms, always to burn the amethysts to citrine and to split off the points of the crystals for facetting. The facetting was normally done abroad.
IT BECOMES PROFESSIONAL
The companies Willi Guerner, Jaghetti and Ledur from Estrela city began a new cicle in the garimpo from 1970 on: they bought the mining rights of small claims, 50 per 30 meters wide, and mined the amethysts there with machines to speed up the production.
People told me that, on one occasion, the old "Bastião", not much convinced of the "business with the stones", sold the mining rights of a claim 20 per 40 meters wide for about 500 "cruzeiros" to one of these companies, for a period of 3 years. There appeared so much amethyst that the claim paid off in the first week ...
This mining right selling stopped in 1985, but long before, Nelson Silvestre, his wife Érida and the children Gilberto, Alencar and Rosane began extracting amethysts by themselves. In the beginning it was with the pick but then, in 1980, the Irmãos Lodi Company, a traditional and important wholesaler of precious stones of Soledade city, financed a machine, which was paid in stones. After this first equipment they bought a truck, a trator-de-esteira and other machines who are used today. Nelson Silvestre and his wife Érida retired some time ago, and today their children are running the garimpo.
DESCRIPTION OF THE GARIMPO
The place of the garimpo doesn't distinguish itself from the surrounding landscape. The ondulating terrain there is typical for these upper lava flows of volcanic rocks that cover Paraná basin in southern Brazil. There appears a thick single lava flow whose upper vesicular level is completely altered to reddish clay. The lava flow has 4 distinct levels:
General view of the garimpo today.
The first is an upper level, 3 to 5 meters thick, with red soil and organic matter. Much of this is the result of creeping processes and bears not a single geode with amethyst. The material of this level is separated to cover, later, the mined places.
The second, beneath the soil level, has a thickness of 8 meters and more and bears the geodes with quartz and amethyst. These geodes have a diameter up to 60 cm, but the average size is smaller. The outer crust of the geodes is made up of quartz and can be thick, with 5 or more centimeters, and shows external corrosion features due to intemperism processes. Agate also ocurrs, but is rare and truncated, so you can't saw them for commercial purposes. Many geodes are completely filled up with quartz and this material is discarded. The amethyst crystals reach a height of 4 - 5 cm, the average material is 2 cm.
Detail of the mined level
Finally, the base level is called "laje", a dense rock without alteration and geodes, typical for the main level of the lava flow. Here you don't have tuffs, pillow lavas, complex flows and other features who appear, for example, in some flows in India and New Jersey.
When operating the garimpo, the altered rock, mainly clay, is removed with machines and the geodes which appear, often broken, are collected by hand, immediately classifying the pieces by quality.
Amethysts already classified in the garimpo.
The old front of the garimpo where they plan to mine the third level now
Apple trees and, in the back, araucaria trees.
The only mineral mined is amethyst. Economically not important are the agates and the different quartz forms. In this way, there are two main products:
a) Plates for collection: amethysts on geode fragments with diameters up to 20 cm, burned to citrine or not.
b) Points, as they called the individualized quartz crystals. They could be:
b1) clean, which are sold with their natural color for facetting, and
b2) half-clean, which are burned to citrine to use the piramides of the quartz crystals.
When the amethysts arrive from the garimpo, they are first washed with high pressure in an instalation specially designed for this.
Washer for amethysts
View of the stove (in the back) with plates of burned amethysts in the barrels, ready for sale to the big precious stones dealer.
A big table with burned amethyst plates, ready for sale. At left, Mr. Nelson Silvestre. Right, his son Gilberto José Silvestre, who runs the garimpo now.
Detail with the different colors of the citrine plates.
Very much of the production of the garimpo is sold directly to the big precious stones wholesalers in Soledade city, which come to the garimpo to buy. Much material is sold to small enterprises in Lajeado and Estrela cities which buy 500 or 1000 kilograms of points to hammer out the points of the burned yellow quartz crystals. These points are later exported for facetting.
ARE THERE MORE MINES IN THAT REGION ?
Other families also have amethyst mines in the Caxias do Sul county, as the Fiorini and the Lize. In Parada Cristal locality is another garimpo. One more you will find in São Francisco de Paula town, but it is not producing now and its owner buys stones from the Silvestres to burn there.
AND THE PRISMATIC PYRAMIDAL APOPHYLLITE ?
You see, the mineral who started this Geo-Reportage didnt appear. I showed to Gilberto, in the garimpo, pieces with different zeolites: chabasite, scolecite, epistilbite, laumontite, stellerite and, of course, some apophyllites, but he didnt recognize any of them. But there are zeolites in that region: some rocks at the entrance of the garimpo showed mordenite and calcite, a paragenesis who include, always, chabasite, heulandite and stellerite. But these minerals do not sell like amethyst, of course. If you don't find a really good zeolite ocurrence, with many good pieces ocurring in bigger geodes, it's not possible to open a mine for that. Of course, even in India the zeolites are collected in crushed stone quarries. I never saw a report about a zeolite mine.
Anyway, discovering and visiting this mine was really interesting, and I loved to share this story with you.