by Allan Taylor

Created on: April 06, 2011   Last Updated: September 27, 2011

The gemstone region of East Africa is exotic and relatively new compared to the long established gemstone regions of South East Asia and Brazil. It extends from the island of Madagascar (Malagasy) in the Indian Ocean to mainland Mozambique then northward through Tanzania and Kenya.

Notable developments have been the discovery and marketing of Tanzanite, a new vivid blue variety of the mineral zoisite, and likewise the promotion of the emerald green variety of grossular garnet, called  Tsavorite, from localities in Keyna and Tanzania. Both these new gemstones have limited production and so command high prices. These gems are the icing on the cake. Many more gemstones are available from this little frequented region.

The island of Madagascar has a reputation for producing valuable gemstones. It provides some fine sapphire and ruby in small size rounds and ovals of 1 to 2 carats. The sapphire is a bright royal blue and the best sell for about $800/carat. Ruby is a lively red at $200/carat and pink sapphire at $100/carat, also fine emerald in 2 to 5 carat size sells at $1000/carat. Much of the gem cutting is done in Antananarivo, the island capital.

Garnets of note are the green and fiery demantoid in 1 to 4 carat size and the orange spessartite in larger sizes at $100/carat. Large pink tourmalines (rubellite) to 50 carats sell at $60/carat.

More of interest to collectors are apatites of fine blue to green color, the best selling at $50/carat. Apatite has the low hardness of 5 on Moh’s scale and forms hexagonal prisms. The blue stones show blue/yellow dichroism. Other faceted stones from the island include alexandrite, iolite (violet), orthoclase (yellow), golden beryl, excellent aquamarine, almandine garnet, citrine, amethyst, whilst cabochon material includes fine scapolite and sillimanite cats eyes, bloodstone, labradorite, ruby and apatite.

Returning to the adjacent African mainland,  Mozambique is a source of beautiful orangey-red spessartite garnet, of multicolored tourmalines and fine aquamarines.

Gem tourmaline grows as small (2 to 5 cm long) prisms having trigonal symmetry. The lively multi-colored stones are the alkali-rich ones low in iron content. Faceted gems are mostly of 1 to 4 carat size. The O-ray of tourmaline (viewed down the prism) has the strongest color so the red, pink, yellow, lime-green, green and blue gems are cut with the table facet perpendicular to the length of the prism to get maximum color intensity. This means

• 1
• 2
• 3
• 4
• Next Page >>