Can Tsavorite be used as an indicator mineral Tanzanite Exploration?

  Left to right: 4.8ct Tsavorite, 3.0ct Tsavorite, 2.4ct Tsavorite, 4.5ct Tsavorite and 6.8ct Tanzanite

Left to right: 4.8ct Tsavorite, 3.0ct Tsavorite, 2.4ct Tsavorite, 4.5ct Tsavorite and 6.8ct Tanzanite

Can Tsavorite garnet be used as an indicator mineral for Tanzanite much the same as garnet, ilmenite and olivine are used as indicator minerals for diamonds?

Farfetched? Let us see…

Land-based diamond exploration uses the presence of the dense minerals, garnet, ilmenite and olivine minerals as an indicator for the presence of kimberlite, which we know as the source rock for diamonds. Exploration geologists use these minerals because they are hard and dense and they are common minerals found in the kimberlite rock. These minerals are also more common than diamonds.

What do we know about Tsavorite and Tanzanite? Well, Tsavorite is rarer than Tanzanite. And the scale of the mines producing Tanzanite are much larger than the smaller scale Tsavorite mines, and this results in significantly more Tanzanite. The amount of discovered crystals per pocket also favors Tanzanite.

But what about the actual surface area exposure and deposits of Tsavorite versus Tanzanite? From one of my previous blog post Origins: East African Tsavorite (23 April 2017); we can see that known Tsavorite sources between Kenya and Tanzania cover a region way larger than the single Merelani Tanzanite source.

We also know now that Tsavorite and Tanzanite are geologically related as we saw in my previous blog post The Family Tree: Tsavorite and Tanzanite (7 May 2017).

If we use the same proven concept for diamond exploration, we know that Tanzanite is younger and is found in the graphite-rich Tsavorite garnet-bearing host rocks. Tsavorite and green garnet is hard and dense and is preserved near its hardrock source. Can exploration geologists now use the Tsavorite green garnet as an indicator mineral for Tanzanite? I believe so.

Okay, great idea, but what is the point if Tanzanite is only found in one place, you ask? Ask Bruce Bridges from Bridges Exploration about the Tanzanite and blue zoisite he found on his Tsavorite Mines in Kenya sometime…