Ruby Zoisite was first discovered in Austria in 1805 and was named for Baron Sigmund Zois, the naturalist who identified the mineral composition as a new find in the mineralogy world. The better known east Africa deposits were first documented in 1904 by a German military commander and scholar who collected the material named after himself, "Merkerstein." His work was never published and the location was lost. Around 1949, these "ruby-in-zoisite" deposits were rediscovered in Tanzania, mistakenly thought to be valuable for the ruby. With all three components being extremely dense metamorphic rocks, early miners found it impossible to profitably separate the ruby from the zoisite.
Although a very few gem quality rubies have been found, unshattered by its matrix, African Ruby Zoisite has gained popularity in the jewelry making industry, also known as Tanganyika Artstone. The majority of what we see on the market today comes from the Longido mine located at the foot of Mt. Kilimanjaro in Tanzania, Africa. Very plentiful, this ruby zoisite has a combined Mohs hardness of 5 to 7 and most of it takes a good polish.
Flowers carved of Ruby Zoisite from Longico Mine, Tanzania, Africa. Notice the crystal structure on the bottom left flower (upside-down). -Dale Armstrong, private collection.