Rectangular Base In Imperial Egyptian Porphyry

Small rectangular base in pre-polished Egyptian imperial red porphyry.
Can be worked to a mirror polish.
Length: 5 cm. Depth: 3.5 cm. Width: 1 cm.
(Small chips, unmachined asperity under the base).

Egyptian imperial poprhyre is particularly rare: only Roman and then Byzantine emperors could obtain this purple rock, the exclusive property of the Emperor (fiscus caesaris).

The purple color of the stone was associated with "Tyrian Purple", the most expensive dye of antiquity.
This rock was all the more rare and precious for being found in only one place on Earth: the Mons Porphyrites, located in Egypt's eastern desert (Jebel Dokhan). After the fall of the Roman Empire, the exact location of the quarry was "lost" for almost 1,500 years, before being rediscovered by explorers in the 19th century without ever being re-exploited.

Porphyry is one of the hardest rocks on the planet (index 7 on the Mohs scale, close to quartz).
In ancient times, it was almost impossible to cut with conventional iron tools. Its extraction required special hardened steel tools and months of emery polishing to obtain a mirror-like sheen. The production of a single 5-metre column took several years of uninterrupted work by an entire team of elite cutters. The cost of transport from the remote quarries of the Egyptian desert to Alexandria and then Rome was so high that a cubic foot of imperial porphyry was traded at the exorbitant price of 250 denarii - the monthly salary of a skilled worker! (for a piece barely 30 centimetres in size).

Because of this difficulty, new blocks stopped being quarried after the 4th century. Almost all the porphyry we see today in churches and museums (columns, basins, sarcophagi) has been reused from Roman-era pieces.