Quebracho is a collective name for three subtropical tree species growing in South America. The word "quebracho" comes from the Spanish quiebra-hacha – "to break an axe". The name comes from the very high hardness of the wood of these trees.

Quebracho is an evergreen tree shaped like a weeping willow. It can be from 10 to 30 metres tall. Quebracho wood is used widely: in construction, for furniture and household items, as well as for art. Quebracho trees grow in northern Argentina, Brazil, Paraguay and Bolivia. Two types of quebracho are best known for their extremely hard and heavy wood (density up to 1300-1400 kg/m³). Red quebracho (quebracho-colorado), the darkening core of which is difficult to work over time, and white quebracho (quebracho-blanco), which has a beautiful yellowish-white hard wood. The hardness and resilience of those trees has become a proverb. When people want to express their admiration for an unbending, courageous man, they compare him to the quebracho tree.

Speaking of quebracho, one cannot but recall the name of Stepan Erzia, Russian and Soviet artist, sculptor, representative of the Art Nouveau style, distinctive sculptor that worked with quebracho wood.
From 1927 to 1950 the sculptor lived in Argentina, where he was called "cowherd" (Spanish: "hombre de la vaca") for his simple way of life.
In 1927, Erzya was the first to use quebracho in artistic works. Prior to Stepan Erzia, no one knew how to process this wood to make amazing works of art. Once at the wharf Stepan Erzya saw large driftwood of some dark wood being loaded. At first sight the sculptor was surprised by the power, bizarre shape and unexpected, unusual colour of the quebracho tree. Even the bark had a special relief, and the sculptor noticed this peculiarity at once. He tried to work the blocks brought from the wharf and immediately realised that the stubbornness of this wood would be hard to break. The tools suitable for working with marble were not suitable for quebracho. Stepan Erzia invented new mechanisms to move the parts of the trunk and treat their surface with compressed air. Erzia adapted for work with unyielding material a milling machine with many attachments, and later the artisan began to use a powerful pneumatic drill; he invented a special composition of glue, which he used to join separate parts of compositions, as well as wood paste, which included the finest wood shredding.
Erzia covered with paste many of his works or separate parts, creating a perfectly smooth polished surface.
The master used the burls on the tree as material for his sculptures. The vital force, frozen in the groves of the tree, actually suggested to the sculptor expressive images. It is not for nothing that the Argentine press called the sculptor «conqueror of quebracho»: from the many scattered pieces, fastened with his own handmade glue, the author managed to create images of an extraordinary emotional intensity with a powerful, amazing energy. Not the least role in this was played by the creative technique of the seamless integration of unprocessed natural fragments into the composition. Erzia brought the obvious technical solution to the logical end– polishing the surface treated with a drill machine to a mirror gloss; it contrasted mirror-like polish of the treated surface (most often the human face and body) of the wildness of the coarse wood, usually depicting hair or folds of clothing. The idea, embodied long before him, and then by him in marble, turned out to be surprisingly interesting when applied to quebracho.

Argentines respectfully called the sculptor «Conqueror of Quebracho», because even the Indians could not handle it. Erzia clearly explained why he preferred wood as a material to marble and clay. He said, “A tree is a living organism that is old and has blood flowing through its veins. Working with wood, the sculptor does not feel the passivity of the material; he feels its warmth, like a living material. The creator can continue and breathe new life into it”.

For a quarter of a century, Argentina became home for Erzia. Here he discovered giant trees with hard wood and fell in love with quebracho and algarrobo, created the amazing sculpturesque world, inhabited by exceptionally beautiful women, handsome men, biblical characters, proud warriors. Their creator long ago has been dead, and they, his children, continue to radiate powerful energy, warmth, kindness. It can’t be put into a formula, it is hard to describe, but you can feel it.

As a result, the works of the Russian sculptor were forever inscribed in the history of art, not only of Russia and Argentina, but also of the entire world. 

The exhibition «In dialogue with Chaco» dedicated to the work of one of the most original sculptors of the 20th century - Stepan Erzia (Nefyodov) is opened in the museum «Collection».

The thematic program includes a tour through the exposition and watching the documentary of Andrey Novosyolov “The Return of Genius” (2016, 25 min) dedicated to the creative biography of Stepan Erzia. Visitors can sign up for an excursion “In dialogue with Chaco» and documentary film “The Return of Genius” on the museum website in the section “Contact Information”.

Ref.: https://otvet.mail.ru/question/13109330
https://azbukametalla.ru/entsiklopediya/k/kvebrakho.html
https://grillspro.ru/product/quebracho-%D1%83%D0%B3%D0%BE%D0%BB%D1%8C-%D0%B8%D0%B7-%D0%BF%D0%B0%D1%80%D0%B0%D0%B3%D0%B2%D0%B0%D1%8F/
https://dzen.ru/a/YEdul7hhPB270Kv6
https://antiqueland.ru/articles/1333/