INTRODUCTION
Minerals are an important component of the resource base of a country. Their systematic exploration and development bring socio-economic progress and help in achieving self-reliance. Gemstones are the minerals which are valued for their beauty and rarity and have been treasured since the dawn of history for personal ornament and as precious symbols of tribute, wealth, power, and prestige. The study of gems is absorbing interest, not only to those whose business is to buy and sell jewellery but to the common men and women for their own personal interest and liking. Gemstones are rare and not evenly distributed throughout the world. Some areas seem to be favoured with an abundance of gem species while others are totally barren.
Each gem deposit is a product of a complex inter-play of different geological processes which have taken millions of years to produce them. Most of the gemstones have characteristic geological environments for their occurrence and they require specific means and methods for their exploration.
Over the past decades, the gem business throughout the world has seen unprecedented incursion of synthetic gems in international market making it difficult for most of the potential buyers to distinguish between a natural and a synthetic stone. Similarly, there are problems to select and explore the areas which may be geologically most favourable to host different types of gems and precious and semi-precious stones.

To answer some of these questions, the IRD and the University of Dar Es Salaam in collaboration with the SEAMIC, the Ministry of Communication, Science and Technology, the Geological Survey of Tanzania and the French Embassy in Tanzania is organizing a three-days workshop on "Gemstones: Their Geology and Gemmology" from 6 to 8th October 2009 at The University of Dar Es Salaam, Department of Geology, Dar Es Salaam.
This event is supported by IRD (Département Soutien et Formation: http://www.ird.fr/fr/science/dsf/; Département Expertise et Valorisation :http://www.ird.fr/fr/science/dev/) and IRD in Eastern Africa and Madagascar (http://www.ird.fr/fr/monde/afrique_est_australe_Oindien.htm)
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WORKSHOP OBJECTIVES
The main objective of this workshop is to present new data and information on some broad aspects of gemmology. In the process of doing so, the organizers intend to present an overview of new trends in geology and gemmology and the effects of modern technology in the search and sale of gemstones and to suggest areas where future work may be of value.
CONTENTS OF THE WORKSHOP
This workshop is designed to provide some basic reference material, procedural techniques and ideas for those who have either, an academic or business interest in gems and gemmology. Included will be such topics as : geological and geographical distribution of gemstones; genesis and classification of gemstones; study of corundum and emerald deposits; gemstone-bearing pegmatites and other rock suites; study of vanadian garnet ("tsavorite") and vanadian zoisite ("tanzanite"), corundum and emerald deposits of Madagascar, mineralogical and gemmological features of some common gemstones; an introduction to techniques for differentiating between a natural and a synthetic stone, microscopic examination of corundum and emerald from all type of deposits, and cutting and polishing gemstones.
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