Onyx
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Onyx is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. Sardonyx is a variety with red to brown band
Onyx with concentric banding
Cabochons of red onyx, also called sardonyx
Black onyx with white streaks
The Gemma Augustea is a Roman cameo produced 9–12 AD and carved in a two-layered onyx gem (19 × 23 cm).
Alabaster
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Alabaster is a soft rock used for carvings and as a source of plaster powder. Archaeologists, geologists, and the stone industry have different definitions for the word alabaster. In archaeology, the
Onyx
…usage it refers to color pattern not band structure. Onyx, as a descriptive term, has also been incorrectly applied to parallel-banded varieties of alabaster, marble, calcite, obsidian, and opal, and misleadingly to materials with contorted banding, such as "cave onyx" and "Mexican onyx". Onyx comes through…
Calcite alabaster: The tomb of Tutankhamun (d. 1323 BC) contained a practical objet d’art, a cosmetics jar made of Egyptian alabaster, which features a lid surmounted by a lioness (goddess Bast).
Alabaster artefact: A composite bust of the Emperor Septimius Severus; the head is marble and the bust is alabaster.
Alabaster windows in the Church of Santa Maria la Mayor of Morella, Spain (built 13th–16th centuries)
Alabaster workshop in Volterra in Tuscany, Italy