Tuesday, November 3, 2020

ONYX - The translucent colour

In November we are celebrating Colour of the Month #15, Onyx - The translucent colourI will go through the origin, chemical composition, varieties and colours, and uses and applications. I had the chance to experiment with a green variety of the Onyx stone during my residency/teaching experience in Argentina. 

Photo credits:
Photo credits: Artifex London. Egyptian Jar early dynasty wikipedia

Since ancient times many civilisations have used Onyx; black and green for traditional, cultural and spiritual practices and activities. These ancient stones were highly prized for burials and ceremonies; shields and armours; amulets affixed to swords. 

Photo credits: Artifex London. wikipedia

Onyx is a triangular crystal structure; a banded variety of the microcrystalline quartz called chalcedony and has a hardness of 6.5 to 7 in the mohs scale. The bands, which are characteristic of this mineral, form a juxtaposition of different colours parallel to one another, as opposed to the more confusing banding in agate stones.

Photo credits: Artifex London. Tinostone.com

These distinctive stripes/bands or patterns occur because of the deposition of silica in the gas cavities of lava. This semi-precious stone is found in various regions of the world. 

Photo credits: AD Classics Barcelona Pavilion by Mies van der Rohe

The colours of its bands and circle patterns range from black to almost every colour such as honey, green, yellow. One of the varieties of Onyx is called Sardonyx, in which the bands are shades of red. Black onyx is the most common and famous variety. 

Photo credits: Artifex London. Yellow translucent Onyx

Photo credits: Artifex London. Yellow translucent Onyx

Onyx stone when it is veneer cut a few millimetres thick, it becomes translucent. The degree of translucency depends on the thickness of the slabs and panels cut for interior and architectural design

Photo credits: Egyptian bowl old kingdom. Artifex london

It is mentioned in various historical texts and documents; and it was the first semi-precious stone mentioned in the BibleThe use of this stone is as ancient as the early Egyptian civilisation. It was used for stone carving, jewelry, pottery, sculpture to represent gods, for ceremonies and burials. 

It was also known to the ancient Greeks and Romans. For instance, Pliny the Elder mentioned in his Naturalis Historia, Onyx and various artificial treatment techniques to imitate it. 

Photo credits: Artifex London. blog Lynn Byrne

Onyx stone is part of the gemstones used in ancient Egypt, which include minerals, rocks and biogenic materials. By biogenic materials I mean all the substances or products made by or of life forms. Some examples of these materials used as gemstones or for pigment include amber, corals, ivory, pearls, shells, etc. 

In Egyptian archaeology, almost all the objects with gemstones come from royal or elite tombs. Rock and mineral varieties do not deteriorate over time, instead biogenic ones may not survive in archaeological records due to atmospheric agents. 

Ancient Egyptians chose to work and use certain gemstones not only for the appearance but also for the symbolism of the colour and the spiritual and energetic properties. 

Photo credits: Studio Laura Daza. Artifex London. wikipedia

Green Onyx is a stunning translucent stone; vitreous when polished, fractured surfaces have a dull or waxy luster. It is colourless when grinded, therefore it was not suitable for pigment making nor painting. It can appear to be white, grey, bluish or any colour due to the minerals that are embedded in it. 

I had the chance to experiment with this stone. It is very soft to break and grind. Unfortunately, the more you grind the more the colour starts to disappear becoming white. That is why in there are no historic records which evidence the use of this stone as pigment. South American green Onyx was usually used as plinths for Art Deco decorative objects and sculptures, also used as materials for wall and surface decoration.

Photo credits: Tinostone.com. Mies van der Rohe Barcelona Pavilion

Photo credits: guardian.co.uk. Mies van der Rohe Villa Tugendhat 

Architects such as Mies van der Rohe favoured Onyx in different colours and varieties to depict and embellish his designs. His buildings, houses and pavilions are filled with stunning banded and patterned stones. A perfect example is his Villa Tungendhat in Czech Republic.  


Photo credits: Assouline-Lichten and slash objects, Chairish.com, Overstock.com, Greyhammer.com.org, TheLine.com, Eye-swoon.com, Burkedecor.com 


Aston, B.G. J.A. Harrell and I. Sahw. "Stones" Ancient Egyptian Materials and Technology. Ed. P. 

T. Nicholson and I. Shaw. Cambridge: University of Cambridge Press, 2000. 5-77.

"Onyx" gemdat.org. Retrieved 22 August 2015.

Stone in Ancient Egypt by James A. Harrell, PhD Professor of Geology