Rock
Giallo antico
Giallo antico
Rome's most prized yellow stone: the Tunisian ‘marble’ first found for Numidian kings, which lit up imperial floors in gold.
Also known as: Marmor numidicum · Numidian marble · Antique yellow
- Popularly: Natural stone (building and decor)
In short
Giallo antico (Italian for “antique yellow”) is an ornamental stone the Romans called “marmor numidicum” (Numidian marble), ranging from deep yellow to almost white and veined in reddish and brown. It was quarried at Chemtou, near the ancient city of Simitthus in today's Tunisia. It counted among the most precious marbles of the Roman Empire, although scientifically it is not a marble but a compacted, recrystallised limestone.
Photos
How does it form?
Giallo antico is a limestone. Fine-grained sediments of calcium carbonate built up, were buried and became compacted. During this process, called diagenesis, the grains largely recrystallised, and the stone gained a dense, crystalline structure that shines like marble when polished. Even so, traces of the small rounded grains (peloids) of the original sediment can still be made out.
Later the stone was broken in places, and the angular pieces were cemented again by white, coarsely crystalline calcite. That is why brecciated kinds occur alongside the even, single-coloured ones. Slender iron-bearing veins and black manganese oxide dendrites enrich its colour and pattern.
What is it used for?
- Numidian and Roman architecture: The Numidian kings were the first to use it, in the 2nd century BC. In Rome, Emperor Augustus used it lavishly in his house on the Palatine Hill and in the Forum of Augustus. It appears together with pavonazzetto in the floors of Trajan’s Forum.
- Inlaid stone floors: In floors made of differently coloured stones cut and fitted together into patterns (opus sectile), the yellow of giallo antico stands out; Hadrian’s Villa at Tivoli and the palace remains on the Palatine are examples.
- Economic history: The stone is listed at a high value in Emperor Diocletian’s Price Edict of the early 4th century, which shows how sought-after it still was.
- Today: Because the ancient quarries were worked out, giallo antico is known as pieces from old buildings and as collection specimens; the quarries and museum at Chemtou can be visited.
Where is it found?
Giallo antico was quarried from the marble hill of Chemtou, beside the ancient city of Simitthus in Jendouba Governorate in north-western Tunisia. Next to the quarries stood a stone-working complex of more than 3,000 square metres and a water system that brought water from more than 30 km away. Finds from the excavations, including fragments of decoration from the monuments of the Numidian kings, are now displayed in the Chemtou Museum.
The famous Corsi collection of decorative stones at the Oxford University Museum of Natural History holds thirteen samples of giallo antico from Chemtou. They show very well how much the colour and texture of stone from a single quarry can vary: some are deep yellow and even, some pale and veined, others brecciated. According to the collection’s experts, giallo antico is the finest of all yellow marbles; only the very best Siena marble can compare with it.
What determines its value?
In antiquity, even, single-coloured kinds were valued above brecciated ones, and “golden” shades and the rare pink kind were especially sought after. Today its value depends on the vividness and evenness of the colour, the look of the veining, the size of the piece and its soundness. Because the ancient quarries were exhausted long ago, giallo antico is known mostly as pieces from old buildings and collections; its historical fame is the main source of interest.
This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.
How to recognise it
- 1
Its colour ranges from deep yellow and golden to pale yellow and almost white, with dark yellow, reddish or brown veins.
- 2
Some kinds consist of angular fragments of different sizes and shades bound together by white calcite (a brecciated look); the matrix between the fragments is red or brown.
- 3
Up close, fine black branching marks of manganese oxide (dendrites) may be visible.
- 4
Being made of calcium carbonate, it fizzes in dilute acid and is easily scratched by a steel knife.
Fakes and imitations
What shops usually don’t tell you:
- The best grades of yellow Siena marble from Italy look very much like giallo antico. In brecciated kinds there is a telling clue: in giallo antico the matrix binding the fragments is red or brown, while in Siena marble it is purple.
- When the Chemtou quarries began to run out in the 3rd century, giallo antico was replaced in Rome by poorer yellow breccias; not every yellow stone in an ancient building is giallo antico.
Myths and misconceptions
MythGiallo antico is a true marble.
FactAlthough it has been called “marble” since Roman times, giallo antico is not a rock transformed by heat and pressure. It is a fine-grained limestone that was compacted and recrystallised after it was deposited (diagenesis).
MythAll the yellow marble seen in ancient buildings is giallo antico.
FactYellow Siena marble looks very much like it, and after the 3rd century Rome used poorer yellow breccias in its place. The colour of the matrix and the texture help tell them apart.
Did you know?
According to Pliny the Elder, the first to bring giallo antico to Rome was Lepidus, who used it for the thresholds of his house in 78 BC.
The stone's value was discovered in the late 2nd century BC, when the Numidian king Micipsa built a monumental shrine at Chemtou.
Chemtou had a high-walled camp of more than 40,000 square metres for the quarry workers, who included convicts and persecuted Christians.
Where is it found?
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- Chemtou (ancient Simitthus), Jendouba, Tunisia · Type localityThe ancient marble hill and quarries where giallo antico was extracted, discovered under the Numidian kings in the late 2nd century BC and worked intensively in Roman times. Today an archaeological site and museum.
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Frequently asked questions
What is giallo antico?
Giallo antico (Italian for “antique yellow”) is an ornamental stone the Romans called “marmor numidicum” (Numidian marble), ranging from deep yellow to almost white and veined in reddish and brown. It was quarried at Chemtou, near the ancient city of Simitthus in today's Tunisia. It counted among the most precious marbles of the Roman Empire, although scientifically it is not a marble but a compacted, recrystallised limestone.
What is giallo antico used for?
Numidian and Roman architecture: The Numidian kings were the first to use it, in the 2nd century BC. In Rome, Emperor Augustus used it lavishly in his house on the Palatine Hill and in the Forum of Augustus. It appears together with pavonazzetto in the floors of Trajan's Forum. Inlaid stone floors: In floors made of differently coloured stones cut and fitted together into patterns (opus sectile), the yellow of giallo antico stands out; Hadrian's Villa at Tivoli and the palace remains on the Palatine are examples.
How hard is giallo antico?
It has a hardness of 3 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 2.7–2.8 g/cm³.
Where is giallo antico found?
Its best-known localities: Chemtou (ancient Simitthus), Jendouba, Tunisia.
How can you tell if giallo antico is real?
Its colour ranges from deep yellow and golden to pale yellow and almost white, with dark yellow, reddish or brown veins. Some kinds consist of angular fragments of different sizes and shades bound together by white calcite (a brecciated look); the matrix between the fragments is red or brown. Up close, fine black branching marks of manganese oxide (dendrites) may be visible. The best grades of yellow Siena marble from Italy look very much like giallo antico. In brecciated kinds there is a telling clue: in giallo antico the matrix binding the fragments is red or brown, while in Siena marble it is purple.
Is giallo antico valuable?
On the “street to diamond” value ladder it sits on step 4 of nine: Fine dimension stone and ore. In antiquity, even, single-coloured kinds were valued above brecciated ones, and “golden” shades and the rare pink kind were especially sought after. Today its value depends on the vividness and evenness of the colour, the look of the veining, the size of the piece and its soundness. Because the ancient quarries were exhausted long ago, giallo antico is known mostly as pieces from old buildings and collections; its historical fame is the main source of interest.
Sources
- Giallo antico · Wikipedia
- Chemtou · Wikipedia
- Corsi Collection of Decorative Stones, no. 24: Giallo antico · Oxford University Museum of Natural History
- Density of Solids · The Engineering ToolBox
- Limestone · Geology.com
External links
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