I hope for the sake of us all as human beings this isn't true, however it is said this was originally made from the ground up remains of Egyptian mummies mixed with pitch and myrrh. It became popular as it had good transparency in oil paint, and was used for glazes, shadows, flesh tones and shading. Apparently it fell from popularity during the nineteenth century when its composition became more generally known to artists.
The modern pigment sold as “mummy” is composed of a mixture of hematite, goethite, clay and quartz; the hematite and goethite determining its colour—the more hematite the redder the pigment—with the others being inert substances that can vary the opacity or tinting strength. This particular pigment comes from the quarries in Lori province of northern Armenia.
In masstone it is a brown/red quite dark in value. For a red earth it is quite a low power tinter however the tints are quite surprising, as when mixed with white the paint's orange undertones become visible and it produces vibrant, orangey flesh hues. Used alongside a cooler red earth this paint would be very useful in describing a multitude of flesh colours, it is really quite warm.
Used thinly, it's transparent nature gives a deep, very warm orange/brown hue.
I can confirm that we would not and never have condoned the grinding up of ancient Egyptian mummies for use in oil paint manufacture, apart from that one last week...
Pigment - PR102
Binder - Linseed Oil
Opacity - Semi-Transparent
Drying Rate - Average