What is cobalt blue?
According to "Pigments through the Ages" a pigment made from cobalt blue glass has been known since the Middle Ages, but an improved form has been established in the 19th century. It was regarded to be durable and even recommended by one painter as a good substitution for ultramarine.
It was new to me that the name cobalt has a connection to the German Kobold which means goblin. German miners searching for silver were often deceived by cobalt or goblin ore that looked like silver, but wasn't. In fact the "Kobold" - after a mountain spirit according to an old tale - contains not only sulphur and arsenic which could be deadly when the ore got melted down, but also cobalt, a metallic element.
This particular color hue was the topic for our Jewelry Artisans Community Oldies but Goodies Challenge, and here's what I picked from the pieces entered.
1 and 8 Ganison Atelier
2 and 4 Jewelry Art by Dawn
3 and 6 Cat's Wire
5 and 7 RioRita