Improvement in the quality of precious stones through microbiological purification and induction of color through ionizing radiation

• Grant number: 98/14685-3
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: November 01, 1999
• End date: April 30, 2000
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Etsuko Ikeda de Carvalho
• Grantee: Etsuko Ikeda de Carvalho
• Company: Trion Tec Radion Comercial Ltda
• City: São Paulo

Abstract

The Brazilian precious stone market is worth millions of Reals and in general they are channeled abroad through the export of crude stones at very low prices; then, after being treated in various ways, they are re-imported. Generally speaking, this treatment adds value of up to ten times the original value of the stone. In terms of economically important Brazilian precious stones, emeralds stand out for their beauty and popularity yet they are marked by the presence of contaminants in their crevices containing iron and sulfur. A number of published papers have indicated that certain bacteria of the Thiobacillus genus are able to attack rocky structures, chiefly concrete, and remove the iron and sulfur, leading to the formation of acids that deteriorate these structures. The present project intends to take advantage of the microbiological method, through use of species of the Thiobacillus genus, to purify Brazilian gems, chiefly emeralds, the contamination of which is related to the presence of sulfur and iron, in order to add value to the stones and decrease Brazil’s expenditure of foreign currency. Similarly, a treatment widely practiced abroad for obtaining topazes, tourmalines and other colored gemstones, using ionizing radiation, is little used in Brazil, to such an extent that stones are sent abroad for treatment, later to be re-purchased by Brazilian jewelers. The present proposal intends to make it possible to treat precious stones using Brazilian infrastructure and installations, lowering the cost and improving the control of irradiated gems. (AU)