Unlocking the Secrets of Anyolite!

By Broden Dymond

Have you ever seen a rock that looks like it has a ruby hidden inside it? If you have, you might have seen anyolite! Anyolite is a metamorphic rock made up of three different minerals: zoisite, ruby, and sometimes amphibole. It is also known by its trade name, “ruby in zoisite.”

Figure 1. Anyolite from Mundarara Mine, Tanzania. Red colored ruby inclusions are visible. Specimen on display at the Idaho Museum of Natural History, Pocatello, Idaho. Photo source Wikimedia Commons.

The Discovery and Trade of Anyolite

Anyolite was first discovered in 1954 in Longido, in northeastern Tanzania. The mine where it was first discovered is still in use today, and anyolite is still exported from Tanzania.

Anyolite is also used in artwork and decorative items. It can be made into sculptures, figurines, ornamental objects, and jewelry designs. Some people also use it in meditation practices because they believe it can help relieve stress and support emotional healing.

But be careful! There is a similar-looking mineral called ruby in fuchsite that can be confused with anyolite. One way to tell them apart is with a hardness test. Fuchsite has a hardness of only 2–3.

The Geology of Anyolite

Anyolite is a metamorphic rock, and it usually has a Mohs hardness of 6–6.5. It contains three minerals that give it an interesting appearance.

The first mineral is zoisite. Zoisite contains chromium, which causes its vibrant green color.

The second mineral is ruby. Ruby is made of corundum crystals, which are a crystalline form of aluminum oxide. The ruby is what makes anyolite especially interesting because the bright red ruby crystals stand out against the green zoisite.

The third mineral is amphibole. Sometimes you can see black specks in anyolite that are made of a type of amphibole called hornblende tschermakite.

Figure 2. Anyolite from Tanzania, Africa. Note rubies. Photo by Hannes Grobe Creative Commons CC-BY-SA-2.5.

The Fluorescence of Anyolite

The cool thing about anyolite is that the ruby in the rock actually glows!

When you hold a UV light to anyolite, the ruby glows. This makes anyolite even more interesting because you can see something happening inside the rock that you normally wouldn't be able to see.

Figure 3. View of anyolite. From the collection of B. Dymond. Photo by B. Dymond.

Figure 4. View of anyolite fluorescing under a UV light. From the collection of B. Dymond. Photo by B. Dymond.

So, the next time you see a green rock with red spots, take a closer look. You might just be looking at anyolite!

About the author

BRODY DYMOND is a member of the Grand Traverse Area Rock and Mineral Club’s Pebble Pups in Traverse City, Michigan. He is from Glen Arbor, Michigan, where he lives. Brody is thirteen years old and will be starting 7th grade at Glen Lake School this year. He has been involved with Pebble Pups for over four years. He has a keen interest in rocks and fossils, and also enjoys being outdoors, biking on trails, robotics, engineering, art, gaming, and Legos. He is currently a Scout from Troop 131 in Suttons Bay, Michigan. He is a program assistant with the Pebble Pup program.