Serie Level

1

Izabella Rebeka Márkus#, 1Ferenc Kristály,

1

Norbert Zajzon, 2Sándor Nagy

1 _{Institute of Mineralogy and Geology, University of Miskolc,} # _{[email protected]} 2 _{Institute of Raw Material Preparation and Environmental Processing, University of Miskolc}

Key words: quartz sand, rutile, zircon, monazite, Ti-oxides

INTRODUCTION

Fehérvárcsurgó is a locality in Central- Hungary, siutated NW from the town of Székesfehérvár. The quartz sand from this locality is known since the end of the 18th century and used for glass manufacturing (Thamóné Bozsó and Baloghné Bozsó 2008), but the industrial scale extraction began only in 1961 (Kun 1989). The white silica sand contains 93–96 wt % of SiO2

and low amount of Fe-minerals, total Fe2O3 content being between 0.24–0.89 %

(Kun 1989), which makes it proper raw material for glass industry after refinement.

GEOLOGICAL BACKGROUND

The late Pannonian quartz sand is situated in the Mór-trench, which separates the Bakony and Vértes mountains. The carbonatic rocks of the Triassic substrata surround the region, which in the upper Pannonian was a closed lagoon and coastal plain (Kun 1989). The quartz-sand, formed in the nearest 300–400 m width zone to the one-time beach, is of glass-sand quality and the sand formed in the farther zone is of foundry quality. The Pannonian-beds are 80–100 m thick (Varjú 1966), the

lower 2/3 is built up of clay and just the upper 1/3 is quartz sand.

The quartz-sand is enriched in heavy- mineral fraction, being undesirable for the glass-sand production. The utilization as a glass industry raw-material requires the separation of heavy- and rare earth minerals. The waste becomes a form of enrichment of these minerals and gives a secondary raw material for critical elements (Nagy 2013).

MATERIAL AND METHODS

The samples were prevailed from the waste material of the glass-sand production plant. The heavy-mineral fraction was separated on the basis of density from the quartz. The obtained fraction was divided to sub- fractions on the basis of magnetism. They were separated to sub-fractions with weak field magnetic separation (0.1 A, 0.5 A, 5 A). In the next step the residue was separated based on density, we obtained a fraction lighter than cca. 4 kg/dm3 and a fraction heavier which later was further divided, based on conductivity. We performed optical microscopy, X-ray powder diffraction and scanning electron microscope analysis combined with energy

94 dispersive X-ray spectrometry on the samples. We performed stereomicroscopy observation during the preparation of samples for electron microscopy. We identified first the grains based on their morphology and color, and then we determined the chemical composition by SEM+EDS. From each sample we selected mineral grains of different color and shape. These grains were placed on adhesive carbon foil for scanning electron microscopic investigations.

RESULTS AND DISCUSSION

The most frequent mineral was the ilmenite, followed by rutile in the samples. The yellow colored, translucent staurolite grains were also present in each sample. The non-magnetic fraction resulted from the magnetic separation at 5 A has the most diverse composition, beside the ilmenite and rutile, it contained staurolite, amphibole, epidote, garnet, zircon and monazite. The nonmagnetic fraction which was lighter than 4 kg/dm3 contained a few grains of ilmenite, rutile, staurolite and was more abundant in quartz, kyanite, tourmaline and amphibole. The magnetic samples resulted from the magnetic separation at 0.5 and 0.1 A shoved similar composition but with different ratios of ilmenite and rutile, some quartz with a few grains of zircon. In the sample lighter than 3 kg/dm3 besides quartz we identified chlorite, staurolite, clay-minerals and few rutile grains. In the samples lighter than 4 kg/dm3 we identified corundum, rutile, staurolite and monazite. The mineral grains in most cases were rounded, anhedral, except partly for the zircon grains, the ilmenite, of which corners and edges were rounded but the ditrigonal crystal shape could be recognized (Fig. 1.) and the tourmaline, which was elongated, ditrigonal prismatic. Based on their chemical composition we could separate different groups of ilmenite. The first group is which contained just Fe an Ti in 1:1 ratio, next group is which contained

also just Fe and Ti, but not in 1:1 ratio, another group is the ilmenite with significant Mg substitution. Some ilmenite with Mg, Al and Si substitution could be observed also. The Ti-oxides have a few percent of Fe substitution, and in some cases with minor Nb content. The very low magnetite content is an interesting feature in the heavy mineral spectrum of the sand.

Fig. 1. Platy ditrigonal ilmenite with rounded edges and corners (BSE image, whit grains are residual Na- politungstenate)

Acknowledgements: The research was carried out as part of the TÁMOP-4.2.2.A- 11/1/KONV-2012-0005 project as a work of Center of Excellence of Sustainable Resource Management, in the framework of the New Széchenyi Plan.

REFERENCES

BÁROSSY, GY.-NÉ. (1958): The sedimentological investigation of the pannonain quartz-sand from Fehévárcsurgó (Dunántúl). Földtani Közlöny, 88/2, 228- 236.

VARJÚ, GY.(1966):Non-metallic industrial minerals. In Geology of our mineral deposits, 238-312.

KUN, B. (1989): 25 years of the National Ore- and Mineral Mining, 153-166.

NAGY, S., CSŐKE, B., ZAJZON, N., KRISTÁLY, F., PAP, Z., KALICZNÉ, P.K., SZÉP, L. & MÁRKUS, I. (2013): Basic experiments of refuse of glass sand from Fehérvárcsurgó in the interest of recovery of critical elements. B. K. L.-Bányászat,

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NEW MINERALOGICAL AND GEOCHEMICAL RESULTS ON THE OPALS