red chalk
Noun
Meaning
red chalk (uncountable)
An indurated clayey ochre containing iron, used by painters and artificers; reddle.
Examples
On 7 December 2007, a red chalk sketch for the dome of St Peter's Basilica, possibly the last made by Michelangelo before his death, was discovered in the Vatican archives.
Pen and brown ink with red chalk, and grey and brown wash, touched with white (British Museum description).
The red chalk writing of this mineral was one of the earliest in the history of humans.
These were printed in red ink so they resembled red chalk drawings which could be framed as little pictures.