Noun
red chalk (uncountable)
An indurated clayey ochre containing iron, used by painters and artificers; reddle.
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. Source: Internet
Pen and brown ink with red chalk, and grey and brown wash, touched with white (British Museum description). Source: Internet
The red chalk writing of this mineral was one of the earliest in the history of humans. Source: Internet
These were printed in red ink so they resembled red chalk drawings which could be framed as little pictures. Source: Internet