To log this earthcache, send me an email with the answer to the following questions:
1) At the given coordinates, on the ground, it is possible to see an infinite number of tourmaline crystals. Indicate its color, if it is shiny or not, average size
2) From what you see in the place, does it look like a rock resistant to erosion or not?
3) Indicate two characteristics of tourmaline
4) Add a photograph of yourself in the local, or another in which an object can be seen, or your nick on a piece of paper
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What are tourmalines?
It is not really a single mineral in a strict sense, but what is called the "tourmaline group", since it includes specimens that are distinguished not only by their color, but by some elements in their chemical composition. However, many authors speak of this gem as a single mineral, with varieties that acquire different names depending on their color.
There are two possible origins for the name tourmaline. One opinion assumes that it comes from the Sinhalese word "touramalli", which means "various colours", and another opinion attributes its origin to another Sinhala term, "turamali", which means "ash magnet".
Tourmalines belong to the group of silicates, generally within the cyclosilicates, and are usually found as accessory minerals in igneous rocks and eventually also in metamorphic rocks.
Tourmaline Characteristics
The two most notable qualities are the enormous variety of colors, and the fact that the same crystal can present several hues along its main crystallographic axes. Other unusual properties it exhibits are pyroelectricity and piezoelectricity, which earned it the name "ash magnet" we discussed earlier.
Its density varies between 3.02 and 3.07 g/cm3 and its hardness ranges from 7 to 7.5 on the Mohs scale. It has a vitreous luster, a conchoidal fracture, it lacks cleavage, it is fragile, and its line cannot be less than white, because it is allochromatic. It may or may not present diaphanousness depending on the varieties.
Tourmaline is stable over a wide range of pressure and temperature, making it quite resistant to both physical and chemical weathering.
"Chorlo"
The plover is the most common species within the tourmalines. Its name comes from the town of Zschorlau, in Saxony (Germany), where it could be observed in an old cassiterite mine (tin ore) already at the beginning of the 16th century. The first description of this mineral, with the name of schorlein or schörlein, is due to Rülein von Calw (1505), who points out its presence in placer-type deposits in Saxony, associated with gold or tin ores.
Plover is typically black in color, practically opaque except for thin shards. It occurs as bacillary or acicular prismatic crystals, generally hemimorphic, with smooth or more frequently striated faces. In many cases, these crystals present mosaic structures. It is also common for them to appear fractured, curved, and re-welded. The plover is pyroelectric and piezoelectric.
The chemistry of the minerals of the tourmaline group is extraordinarily complex, since the real specimens have intermediate compositions between those of several of the extremes that make up the different series. Plover, whose ideal formula is NaFe2+3Al6Si6O18(BO3)3(OH)3OH, appears forming series mainly with dravite and elbaite and less frequently with uvite and foitite.
Plover is a common mineral, known from several thousand locations around the world. It is found forming part of granites, in pegmatites, in high-temperature hydrothermal veins and in different types of metamorphic rocks.
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