ETYMOLOGY: It comes from the greek "onux" meaning nail.

CRYSTAL SYSTEM: Trigonal.

PRINCIPLE OF FORMATION: Primary / secundary.

CLASS MINERAL: Oxides, quartz group

CHEMICAL FORMULA, MINERAL ELEMENTS: SiO2 + C (Fe, O, OH).

HARDNESS: 7 on the Mohs scale.

FIELDS: Brazil, India, Russia, Asia Minor.

MINERALOGY: A variety of agate, the most important variety of chalcedony (sardine). It is a type of onyx characterized by two or more layers of milky chalcedony and transparent red ruby, although sometimes strong color coat is golden or brown. The black onyx and red-brown is formed by the inclusion of iron and manganese, originates hydrothermally hollow cavities in the rocks.

MYTHOLOGY: The name is mentioned once in the Bible, in Revelation 21: 2, 19, 20, which states that the fifth foundation stone of the "holy city, New Jerusalem," is a birthstone. The red-brown (sardonyx) and black onyx was highly valued in Rome, especially for seals, because it was said to never stick to the wax. The Roman general Publius Cornelius Scipio was known for wearing large amounts of birthstone.

PROPERTIES: It is said that the black onyx, red-brown (birthstone), provides strength and protection, is a stone that attracts friends and good luck, mentally improves the perception and assimilation capacity, gives us stability, confidence in ourselves and in others, it helps us to overcome the pains and brings joy to pass on to others, the black onyx red-brown (sardonyx) overcoming power, strengthens the will, makes us kind and generous.

CHAKRAS: Sacral.

ZODIAC SIGN: Leo.

USES: Jewellery, meditation, collection, ornamental stone.