The Onyx generally has been treated in the chapter on Leo when writing of the Sardonyx; but the stone peculiar to Capricorn is the black, or dark brown, which is generally marked with a decided white stripe across it, or the white stripe may appear in the form of a circle round the centre, in which case it is known as the Lynx-eye Onyx by the natives of India where the finest stones are found.

From very remote ages, particularly in India, the Black Onyx has been considered essentially the stone for rosaries, its attributes being to restrain passion, to give spiritual strength and inspiration, and to be beneficial in the cure of fits. It should not, however, be worn by any one born with Saturn unfavourable in their horoscope, which fact was known to mediaeval astrologers who, in such cases, as mentioned by Marbodus, assert that its wearer would be exposed to the assaults of demons and bad visions by night, and plagued with quarrels, law-suits, and melancholy by day; that it would nullify their labours, and even cause its owners to feel the pinch of poverty (all recognised Saturnian troubles and afflictions), only to be counteracted by the introduction of the Sun's brightening influence in the form of the Sard.