“East African Gems” by Jim Walker

Jim Walker

Jim Walker

Tuesday October 7th, Jim Walker entertained an enthusiastic group of DC GIA members with tales of his adventures in East Africa.

He also fascinated us with information on tsavorite and tanzanite from his mining operation with Campbell Bridges as well as prospecting and mining techniques.

Mr. Walker talked about tsavorite’s earliest discovery in 1961 with Mr. Bridges, and traced it through 1967, when the actual source was discovered in 1967.

He mentioned that the coloring agents for tsavorite are vanadium and chromium, and that a mixture of 85% vanadium and 15% chromium produces the ideal color.


He talked about how their mining operation is sensitive to safety issues and the environment, and has helped set the standard for safe mining in the area. He covered prospecting from the use of termite mounts for spotting potentially gem-rich pockets, to examining geological maps for concentrations of graphite gneiss and limestone to pinpoint areas.

Once the area has been identified, their mining operation lays out a prospecting grid, which is similar to the grid that archaeologists lay out on their site before excavation. The miners dig down to the limestone bedrock, and then break through it to the graphite gneiss below where the gem-bearing reef is located.

Jim talked about the two different types of reefs that tsavorite is located in, a recumbent curve and a plane. He said that they try not to do open mining, and use ventilation and supports in their tunnels; concepts that are not widely used in East Africa except by their mining operation. He also pointed out that their miners work the gemmy reefs by hand so that they don’t damage the tsavorite crystals. Once the tsavorite is recovered, it is sifted in water using a gravitation method, then graded and cut in house.


Mr. Walker topped off the evening by suggesting that AGTA organize a marketing campaign to educate the public and raise market awareness for colored gemstones, not unlike what DeBeers has done for the diamond market. He then shared some of his incredible tsavorite and tanzanite samples with our group. It was a “gem-packed” evening!

Meeting Summary by Etta Marie Dotson, PhD, GG, ISA AM

Photos by Melanie Marts, GG

This entry was posted in Meeting Archives. Bookmark the permalink.

2 Responses to “East African Gems” by Jim Walker

  1. Phanuel kiwinga says:

    hi walker im finding this information really helpful,im a small scale miner from Taita hills with very little knowledge on mining techniques i have thrown my hope in some patrners who experienced and worked for one of the popular mine owned by Joe kihara and none has worked for bridges though,am apealing for directives on how to employ the best techniques and most of all the market for tsavorite.in regard to what stage we are at we are prospecting as yet though all the indication as per the your story are evident giving me more hope on reaching the pockets we have found the vein and carefully sinking with itim at Lualeny ranch its alocation 10kms from bridges mine.regards

  2. Perez says:

    @Phanuel Kiwiga why dont you try and contact Joes Brother for any piece of advise they were really successful and know mining business like no other… i have his deyails if you wish.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s