Agate geodes are treated and stained for the production of handmade artifacts and jewelry, which greatly increases their aggregate value. Unit operations involve storage, sorting, cutting, crushing, dyeing, polishing, washing, and finishing. Substantial amounts of waste materials are produced, which include agate pieces, powders (with or without oils), and wastewaters from organic and inorganic staining procedures. The aim of this work was to quantify the amounts of these waste materials, their characteristics, and possibilities for reuse or recycling in other productivity sectors in the context of the second decade of the 21st century. A review of the theme was carried out and possibilities were analyzed in the light of classic and new technologies.

The aim of this work was to study the use of coal waste to produce concrete paving blocks. The methodology considered the following steps: sampling of a coal mining waste; gravity separation of the fraction with specific gravity between 2.4 and 2.8; comminution of the material and particle size analysis; technological characterization of the material and the production of concrete paving blocks. The results showed that the coal waste considered in this work can be used to replace conventional sand as a fine aggregate for concrete paving blocks. This practice can collaborate in a cleaner coal production.

Commercial coal production in the southern region of Brazil has been occurring since the beginning of the twentieth century. Due to the geological characteristics of the region, large amounts of solid wastes are generated. The aim of this work was to evaluate the use of coal waste to produce concrete paving blocks. A procedure to process the coal waste with the purpose of reducing the sulfur content and changing the particle size distribution of the material to meet the specification of fine aggregates was developed. The methodology considered the following steps: (a) sampling of a coal mining waste; (b) gravity separation of the fraction with specific gravity between 2.4 and 2.8; (c) comminution of the material and particle size analysis; (d) technological characterization of the material and production of concrete paving blocks; and (e) acidity generation prediction (environmental feasibility). The results showed that the coal waste considered in this work can be used to replace conventional sand as a fine aggregate for concrete paving blocks in a proportion of up to 50%. This practice can result in cleaner coal production and reduce the demand for exploitation of sand deposits.