A rare straight sided mortar in Royal Egyptian Porphyry . Height : 21 cm Diameter : 27 cm .
For me the object is Period , Roman , IInd - IIIrd century CE , because of the model , the surface and other Roman comparanda dating from the Roman Period . The shape similar as a mortar found in Pompeii and as the Gladiator Cup now in the MET museum in New-York .

No other stone in Western Civilization has attained the same prestigious status as that of porphyry . It is a stone which embodied the power of Emperors and rulers since Antiquity , and from the end of the Roman Empire represented a means to legitimise and underline the power of any pretender to the throne . Of a deep purple color with flecks of white , the bullet hard volcanic stone was , according to Pliny’s Naturalis Historia , discovered by legionary Caius Cominius in the year 18 CE at a location now called Mons Porphyrites (Porphyry Mountain), in the eastern desert of Egypt . Romans gave the stone a name : “porphyry” , deriving from the Latin word for purple , the color of nobility . With exceptional strength and durability , its intrinsic qualities were perfectly suited to the message of power and authority , but also made it extremely hard to work and carve . Making objects in this hardstone was both political and an artistic statement . After the 5th century , the quarries ceased to be mined and Mons Porphyrites was lost in oblivion . Thereafter , the sole source for porphyry of this type used in Western Europe were ruins from Ancient Rome , imbuing the new works created with a deep spiritual connection to Antiquity .