Mineral. Deposita 31,589 596 (1996) MINERALIUM DEPOSITA 9 Springer-Verlag1996 Mineral processing characteristics of natural zeolites from the Aritayn Formation of northeast Jordan K.M. Ibrahim 1, S.D.J. Inglethorpe 2 1Natural Resources Authority,Ministry of Energy and Mineral Resources, P.O. Box 7, Amman,Jordan 2Mineralogy and PetrologyGroup, British GeologicalSurvey, Keyworth, Nottingham,UK, NG12 5GG Received: 11 January 1996/Accepted: 10 April 1996 Abstract. The inferior grade of natural zeolite ores in comparison to their synthetic counterparts has been iden- tified as a possible factor responsible for the relatively small market share of the former. This paper describes the results of laboratory-scale mineral processing trials car- ried out on relatively low-grade natural zeolite ores from the Aritayn Formation of northeast Jordan to improve their purity through removal of unwanted gangue con- stituents. Appropriate sample preparation and mineral processing methods were selected which utilised contrasts in texture, particle-size, hardness, specific gravity and magnetic susceptibility between gangue and target con- stituents to achieve beneficiation. Sample preparation by autogenous comminution was able to selectively liberate zeolite minerals from the surface of pyroclasts and there- fore was an effective method of pre-concentration. Sub- sequently, using widely-available magnetic and gravity separation equipment, a high-grade concentrate contain- ing 89% zeolite was produced at a recovery of 37% from a lapilli tuff of 47% head grade. the U.S.A., a preliminary study (Mondale et al. 1978) and a later more comprehensive investigation (Mondale et al. 1988) upgraded 10 sedimentary (ash tuff) zeolite deposits, including chabazite, clinoptilolite, erionite and mordenite ores, by standard wet beneficiation methods such as clas- sification (hydrocycloning), gravity separation (wet tabl- ing) and froth flotation. In the majority of these deposits, the zeolite minerals present were less than 0.04 mm in size. Samples were prepared by jaw-crushing to -1/4 inch (-6.35mm) and roller crushing to -20 mesh (-0.85 ram). Crushing to this size typically produced 25-50% material passing - 100 mesh (- 0.15 mm). The present study describes an attempt to improve the purity of relatively low-grade natural zeolites (lapilli tufts) from northeast Jordan using standard mineral processing methods. In particular, the use of petrographic, min- eralogical and physical property data to help plan pro- cessing trials was tested. Appropriate sample preparation and mineral processing methods were selected on the basis of contrasts in texture, particle-size, hardness, specific gravity and magnetic susceptibility between target and gangue constituents. Mineral processing of natural zeolites Eyde (1993) noted that the grade of most commercial natural zeolite ores (zeolite content about 75%) is lower than that of many other industrial mineral commodities, such as kaolin, limestone, glass sand, etc. Eyde identified this deficiency as being partly responsible for the low sales of natural zeolites and the large market share of their synthetic counterparts. However, he suggested that the purity of natural zeolites could be improved using cur- rently available mineral processing technology. Eyde con- cluded that more financial resources within the natural zeolite industry need to be allocated to the production of processed high-purity products which are competitive with their synthetic counterparts in terms of price and performance. To date, only a minor amount of research on the min- eral processing of natural zeolites has been carried out. In Mineral processing: facts and definition A brief description of mineral processing terminology and notation used is given next. The main aim of mineral processing is to remove unwanted constituents of the ore (the gangue) and concentrate the mineral of value (the target ) in a product at high grade and high recovery. The grade is defined as the weight percent of target mineral present in the product, and the recovery is the amount of the target mineral in the concentrate expressed as a pro- portion of the target mineral in the original or head sample (see Wills 1992). Usually, a balance has to be struck between grade and recovery such that a product of the desired grade is obtained from the mineral deposit at an economically acceptable recovery. Another important factor is the yield which is the proportion of the total weight of the head sample contained in the concentrate. Prior to crushing and grinding, the texture of the ore (in