Manufactured Feldspar-quartz Sand for Glass Industry from Gneiss Quarry Rock Fines Using Dry Rare-earth Magnetic Separation

ABSTRACT

Feldspar concentrates, which have important applications in industry, have been mostly produced from pegmatites, granites, and sands from rivers. The metropolitan area of Rio de Janeiro contains major deposits of gneiss rocks which are the basis of crushed aggregate production. These rocks not only contain large amounts of feldspars, but also of mafic minerals. The paper demonstrates the use of rare-earth magnetic separation (REMS) in dry processing of a manufactured fine aggregate from a gneiss quarry. By removing iron-rich components from the low-value fine aggregate, a higher-added value feldspar-quartz concentrate for application in glass industry is produced. It is demonstrated that three-stage separation was successful in reaching the product specifications for use as fluxing agent and stabilizer in amber glass production. In order to demonstrate the robustness of the separation strategy, three different rock types present in the quarry were processed and results demonstrated that REMS is able to reach the manufacturer specification regarding iron content (<0.3% Fe₂O₃ in the product) in spite of the variation in feed composition. An industrial flowsheet on how this technology can be deployed in a plant producing quarry rock is proposed.

KEYWORDS:

• Feldspar
• high-intensity magnetic separation
• dry processing
• biotite
• gneiss

Acknowledgments

The authors would like to acknowledge the assistance of Ms. Jaqueline V. Oliveira from CETEM in the X-ray fluorescence analyses.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Additional information

Funding

The authors would like to thank Mineração Santa Luzia Ltda. for supporting the work, as well as the Brazilian Agencies CNPq [Grant Numbers 310293/2017-0 and 302828/2015-0], CAPES and FAPERJ [Grant Number E-26/203.024/2016] for partially funding the work.