Armenian bole

[1] It is red due to the presence of iron oxide; the clay also contains hydrous silicates of aluminum and possibly magnesium.

Historically, the term bolu or bolus was used only for medicinal earths and Armenian bole was used as an astringent, prescribed against diarrhea, dysentery, and bleeding.

Use for internal medicine may have side effects as the minerals often include heavy metals such as arsenic, cadmium, lead and zinc that can cause toxicity.

As a result, they were coloured red using Armenian bole to disguise the buildup around the teeth.

[5] It is also used in bookbinding for coloring, or applied to the edges during gilding, as a base for the gold leaf and to give the binding a greater depth and luster.