_Purpurissum_ was a _lake_, as is obvious from the account of its formation given by Pliny. The colouring matter is not specified, but from the term used there can be little doubt that it was the liquor from the shellfish that yielded the celebrated purple dye of the Tyrians. _Indicum purpurissum_ was probably _indigo_. This might be implied from the account of it given by Pliny. The austere colours used by the ancient painters were of two kinds, native and artificial. The native were _sinopis_, _rubrica_, _parætonium_, _melinum_, _eretria_, _auripigmentum_. The artificial were, _ochra_, _cerussa usta_, _sandaracha_, _sandyx_, _syricum_, _atramentum_. _Sinopis_ is the red substance now known by the name of reddle, and used for marking. On that account it is sometimes called _red chalk_. It was found in Pontus, in the Balearian islands, and in Egypt. The price was three denarii, or 1_s._ 11¼_d._ the pound weight. The most famous variety of _sinopis_ was from the isle of Lemnos; it was sold sealed and stamped: hence it was called _sphragis_. It was employed to adulterate minium. In medicine it was used to appease inflammation, and as an antidote to poison. _Ochre_ is merely sinopis heated in a covered vessel. The higher the temperature to which it has been exposed the better it is. _Leucophorum_ is a compound of 6 lbs. sinopis of Pontus, 10 lbs. siris, 2 lbs. melinum, triturated together for thirty days. It was used to make gold adhere to wood. _Rubrica_ from the name, was probably a red ochre. _Parætonium_ was a white colour, so called from a place in Egypt, where it was found. It was obtained also in the island of Crete, and in Cyrene. It was said to be a combination of the froth of the sea consolidated with mud. It consisted probably of carbonate of lime. Six pounds of it cost only one denarius. _Melinum_ was also a white-coloured powder found in Melos and Samos in veins. It was most probably a carbonate of lime. _Eretria_ was named from the place where it was found. Pliny gives its medical properties, but does not inform us of its colour. It is impossible to say what it was. _Auripigmentum_ was yellow sulphuret of arsenic. It was probably but little used as a pigment by the ancient painters. _Cerussa usta_ was red lead. _Sandaracha_ was red sulphuret of arsenic. The pound of sandaracha cost 5 as.: it was imitated by red lead. Both it and _ochra_ were found in the island Topazos in the Red Sea. _Sandyx_ was made by torrefying equal parts of true sandaracha and sinopis. It cost half the price of sandaracha. Virgil mistook this pigment for a plant, as is obvious from the following line: Sponte sua sandix, pascentes vestiet agnos.[70] [70] Bucol. iv. 1. 45. _Siricum_ is made by mixing sinopis and sandyx.