第17卷第3期 地质与资源 V01.17 No.3 2008年9月 GEoL0GY AND RES0URCES Sel .2008 Article ID:1671—1947(2008)03—0235—06 CLC Dnmher-P619.23 Document code:A RECOVERY OF FELDSPAR RAW MATERIAL FRoM GRANITE ROCKS FoR CERAMIC AND PoRCELAIN INDUSTRIES Mohamed E1一Omla,Salah Shata (Geology Department,Faculty ofScience,Suez Canal University,Ismailia,PC 41522,Egypt) Abstract:Granite is the main source of feldspar for ceramic and porcelain industry after pegmatite.The problem with granite as a source of feldspar is the presence of mica and iron oxides that cause reducing the strength,hardness and densitv of the ifnal product(1ow quality ceramics).This study presents the results of applying two phases of separation on Zhejiang granite, Southeastern China,in order to improve the quality of the feldspar obtained from this granite.The first phase is gravitational separation to remove the heavy impurities and the ̄econd phase is magnetic separation to further minimize the iron c0ntent. Mechanical property tests are conducted on the feldspar product of 3 samples:raw granite,processed granite I(granite after gravity separation,china clay and quartz),and processed granite II(granite after complete processing.china clay and quartz】.Micro—hardness, strength, fracture toughness and density show sharp improvement in the qualitv of the processed granite relative to raw ode.This improvement is attributed to出e absence of undesired impurities f lnica and heavy arinerals). Key words:feldspar;granite;heavy mineral;processing;ceramic and porcelain industry;Zhejiang Province 1 Introduction The purpose of this work is to separate the raw Alkali feldspars are one of the basic raw materials 0f materials from Zhejiang granites to supply the ceramic and ceramic and porcelain industries.Feldspars are alumina porcelain industries. silicates containing K,Na and a small amount of Ca,and usually embodied in rocks such as granite and syenite,or 2 The Granitic Pluton in Zh ̄iang occu ̄ing in large mass as in pegmatite.In recent years, Zhejiang Province is located in the southeast part of the consumption of feldspar has been increased China.The topography is dominated by low hills with signiifcantly together with the developing and changing small plains in the northern and eastern coastal areas. technology.As pegmatite occurs in very limited quantities Most of the intrusions appear as stocks or offshoots, and very restricted geologic environment(does not meet few as batholiths.The magma has muhisources and the the increasing demands),there is a need to look for 0ther rocks are polygenetic.The granitoids may be divided into rocks as potential reserve for feldspars.A majority of these syntexis and transformed types according to their sources rocks are low feldspar quality,and contain unwanted and ways of emplacement.The Jinningian and Himalayan impurities for ceramic and glass industries. intrusives are mainly of the transofrumd type.Some Granite consists of an important proportion of Yanshanian K—feldspar granites may have the characters feldspar and qua ̄z.Other minerals associated with th0se of the differentiated type_1]. are biotite,muscovite and iron oxides.Genera11v minerals Alkali feldspar granite is very rich in quartz and other than feldspar and qua ̄z have speciifc magnetic potash feldspars but it is a local distirbution;while granite properties and high density.Therefore,it is possible to rock is less in alkali feldspar and in the meantime has a remove them in appropriate liberation size.In this study, regional distribution in many places,which is why it was the possible economical concentration of feldspar from selected to be studied as a material to use in ceramic and Zhejiang granite is aimed. porcelain industries. Receiveddate:2007—05-23;Accepted date:2007—10—14.Editor:ZHANGZhe 236 地 质 与 资 源 2008正 In hand specimen,the studied granite rocks are usually darker than alkali feldspar granite,medium—to coarse—grained,generally with a subhedral granular texture,Both the feldspars and the marie minerals tend to occur in subhedral crystals,whereas the quartz is usually in grayish color,very glassy,and fills areas between other grains.Plagioclase feldspar is usually the most abundant mineral,somewhat coarser than the quartz,and often whitish or reddish in color.Potassium feldspar breaks along planes of weakness in the crystals,forming aat,smooth and shiny cleavages.Quartz also breaks through crystals but as conchoidal fracture instead. Muscovite and biotite have such a perfect cleavage that they break into thin sheets. 3 Materials and Method 3.1 Material Representative samples of granite from Zhejiang Province,china clay and quartz are used in these experimental studies. 3.2 Methods In this work,X—ray diffraction method is used,and crystalline powder diagrams were obtained by a Rigaku D/max一2500 PC X—ray diffractometer apparatus. 3.2.1 Microscopic study Under the microscope,the granite is essentially composed of plagioclase,nfieroperthite,K—feldspars and qua ̄z with subordinate amounts of mica(biotite and muscovite)and sphene(Fig.1).Plagioclase,mainly oligoclase(An 15—20),is the dominant mineral, constituting about 50%to 70%of the rock.Most of the plagioclase crystals contain a small to moderate amounts of orthoclase in antiperthitic intergrowth.Plagioclase occurs in subhedral to anhedral prismatic crystals.Many of the plagioclase crystals are twinned according to the albite and combined albite Carlsbad twinning.Potash feldspar represented by perthite occurs as subhedral to anhedral prismatic crystals.Quartz is found as seeondapy interstitial xenomorphie crystals filling the interstices among the other constituents.It is deformed and cracked where wavy extinction is recorded (Fig.2).Mlea, generally dark and strong pleochroic,commonly contains inclusions of apatite,sphene,iron oxide and zircon. Fig.1 Photomicrograph of granite,showing Carlsbad lamellar twining plagioclase(1ight gray,PL),bordered by perthite(dark gray,P).Qu‘ar【z f Q)is clear white and gray color with tiny biotite inclusions (BI).K~feldspar(black and gray,cross hatched twinning,K) Fig.2 Photomicrograph showing plagioclase partially replaced by serieite(S).Q.artz is anhedral and wavy extension(white and gray,Q). P1eochroic haloes due to radiation..induced damage commonly occur in biotite around radioactive inelusions such as zircon(Fig.3). 3.2.2 Separation procedure Crushing and sieve analyses have shown that 70%or 80%of the particles are Jiberated below 1.2 mm.The sample is divided into four different size fractions in order to increase concentration recovery.The size rfaction larger than 1.2 mIn is not used at concentration tests. r、vo separation methods are tested in order to check if the alkaline content of the feldspar raw material(granite without impurities)is suitable to be used in the ceramic industry. 第3期M。hamed:RECOVERY OF FELDSPAR RAW—MATERIAL FROM GRANITE ROCKS FOR CERAMIC AND PORCELAIN INDUSTRIES 237 Fig.3 Photomicrograph showing biotite strong pleochroism(Bi), with tiny inclusions of iron(I).Radioactive decay in the zircon cr/stal has destroved the biotite lattice near the inclusions,creating dark halo around each zircon(Z). (1)Densimetric separation Three grain size classes(1.2—0.6 Inln,0.6—0.4 mm and 0.4—0.1 mil1)are allowed to set freely in heavy liquid(Table 1).Bromoform is used as dense liquid and tw0 fractions are obtained: (a)light fraction of a lower density than 2.8 g/mL,formed,theoretically,by quartz and feldspar;and(b)heavy rfaction,of a higher density than 2.8 g/mL.The percentages of separated material in relation to the total weight of the sample obtained by densimetric separation are,usually,low and very variable.This may be due to the various diifculties of the procedure. Table 1 Gravity separation for granite 表1花岗岩重力分离结果 The ifrst is the obtainment of a standard and suitable Darticle size for this kind of separation.The grain size has to fulfill two requirements:to be small enough to allow the isolation of the granite minerals from each other and not so small as it will not promote surface tension phenomena be tween the particles and the liquid,thus very fine particles could agglomerate and prevent from separation・ S0.“1e problem in this procedure is how to optimize these two factors to get an effective mica separation. In the other hand,bromoform,the most common used dense liquid.is a very toxic product.Furthermore, the light fractions become completely impregnated in it, thus a light heating is necessary,which produce toxic vapors and lead to loss of the expensive heavy liquid 1々I. (2)Magnetic separation Magnetic separation is the method camed out after gravity separation to separate the undesired material(s) which have magnetic property.In the magnetic separation meth0d,onlv two size fractions are used,namely 0.6— 0.4ram.and 0.4—0.1 mm.The size fraction of 1.2—0.6 mnl is disregarded because the presence of the iron oxide and mica are compacted with the light minerals,hence the machine can not separate them[引.In this work,Jones high—intensity paramagnetic separator 1 300 x 80 A/M is used.Two fractions are obtained:the larger is made of n0n.magnetic“light minerals”,and the other of magnetic one“black minerals”(Table 2). Table 2 Magnetic esparatiollfor granite 表2花岗岩磁力分离结果 4 Optimization of Granite Composition 4.1 Formulation and preparation of granite containing bodies To formulate granite—containing bodies,china clay and quartz(powder)are added.The high quality—burning clays(e.g.china clay)would enhance the cohesion and mechanical strength to the material and provide its sinterability in firing,while qua ̄z would improve the mechanical strength.The preparation of the bodies can be 238 地 质 与 资 源 2008正 schematically described as follows:small blocks of 5 Quality Assessment of the Formulated Ceramics Selected mechanical parameters,such as strength, fracture toughness,hardness,density and porosity,have been used to assess the quality of rock raw material Zhejiang granite,china clay and quartz are crushed, sieved through sieving(100 mesh)independently.Then, the mixtures are formed with following ratio:60%china clay,10%quartz and 30%granite.The mixtures are further grinded in ball mill with a suitable amount of water (granite,G 1)and cmnposite samples(ceramics,C 1 and C2).In other words,mechanical parameters are measured to investigate the effectiveness of separation method on the quality of the product made of the processed granite f0r 24 hours to make slurries using high purity alumina balls as milling media.These mixtures are completely dried in an oven under vacuum at a temperature of 40c《= for 1 2 hours.The dried blends are then crushed with a porcelain pestle and sieved.This method would produce a homogeneous distribution of discrete granite grains through the composition.Twenty drops of a binder additive(polyviny1)was added to 2.5 g of each mixture. This additive is added to make the particles stack together,and to avoid crack of the samples.Then,the mixtures are dried,crushed,and pressed at room temperature to 1.1 ton in the sintered bodies with the dimension of 60 mm×4 miD.X 4 mm.The simplest and most commonly used compaction method is uniaxial pressing of a powder in a die at room temperature to obtain a matrix density in dry air at room temperature. The sintered bodies are then fired to 1250 .The specimens are then polished,with 10,7,and 3 ponl abrasive papers consecutively. Three bodies,natural granite,ceramic一1(treated granite after gravity separation,china clay and quartz) and ceramic一2(granite after“densimetric and magnetic separation”,china clay and quartz)have been formulated. Examination using both the optical microscope and the scanning electron microscope is performed to study the mierostructure of various fired—samples. 4.2 Mineralogy of raw material X—ray diffraction pattern of Zhejiang granite revealed that such granite contains a considerable amount of muscovite and clinochlore beside the essential component of feldspar and quartz.The resultant concentrate after gravity separation followed by magnetic separation consists of feldspar and qua ̄z only.XRD pattern of the undesired impurities indicate that they consists mainly of clinochlore and muscovite,i.e.,the proposed separation procedures are able to separate both mi a a T1d eh1nrit . relative to natural one. The density and porosity of fired samples are measured by the Archimedes immersion technique, involving in boiling water ofr 30 minutes l , .The strength is measured by three—point bending at room temperature (span:30 nnn;croSS—head speed:0.5 mm/rain).The rfacture toughness is measured by the indentation fracture method with a Viekers indentation using a load of 3 N and a loading duration of 1 5 s The hardness is also measured on mirror polished surface by the indentation technique in Vickers microhardness tester for each case a mean of 10 measurements is taken.Fracture toughness is calculated with the forumla given by Evans and Wilsha_w[ . The density of the studied samples increases with progressive subtraction of undesired impurities in granites.On the other hand,it is apparent that,the porosity decreases with increasing of the puriifcation of samples from mica.This may be attributed to the low fomlation of closed pores.Optimum vitriifcation is achieved when the porosity approaches zero.Porosity shows an inverse relation with density,as expected. Scanning electron micrographs exhibit trenches and cracks in the untreated granite samples(Fig.4),while the composite samples prepared from processed granite show no cracks and exhibit dense texture(Fig.5). There is a reduce in micro—hardness of the granite compared with the other two batches C 1 and C2,because the mica grains show very low tie with their neighbor minerals(quartz and feldspar). The increase in strength with progressive substitution of mica—chlorite by quartz is attributed to the function of quartz in the strength of white ware body[ , .as well as the absence of mica.The quartz particles acted as a barrier to crack propagation when a stress is applied, 第3期Mohamed:RECOVERY OF FELDSPAR RAW MATERIAL ̄FROM GRANITE ROCKS FOR CERAMIC AND PORCELAIN INDUSTRIES 239 Also,with increasing purification of granite from undesired impurities,both micro—hardness and fracture toughness would increased considerably.As load applied to the specimens,the three samples display different reaction against the applied loads,where ceramic一2 started failing at a load higher than ceramic一1 and granite. The stress will be concentrated near mica grains and Fig.4 Scanning electron micrographs showing the typical trenches cracks in the granite. Fig.5 Scanning electron micrographs showing formulated granite with interlocked texture and no cracks. thereby increasing strength.The drastic fall in strength in untreated granite confirms the role of mica that is deleterious on strength in a porcelain composition. cause microfracture in the adjacent minerals. 6 Conclusions In this research,an experimental procedure for utilizing the granite as an alternative raw material for ceramic and porcelain industtT is investigated.The results of this study can be summarized as follows. (1)The granite has a suitable content of alkali ofr extracting feldspar raw materials aS an alternate ̄ource of feldspar when pure feldspar(pegmatite)deposits become scarce and may be used as processed raw material in porcelain and ceramic industries.Yet,the existence of mica—chlorite and any other heavy minerals in batches has been found to have a negative effect on the mechanical properties of the ifnal product. (2)From the petrographic point of view,biotite and muscovite are present in subordinate amount.They may embrace radioactive inclusions such as zircon and alunite. So it is very important to remove these minerals due to their harmful effects on the industry,accordingly human USeS. (3)Two separation procedure are proposed to get rid of undesired impurities(biotite,muscovite,clinochlore, zircon,etc.J,namely gravity separation and high intensity magnetic separation. (4)The quality of feldspar concentrate attained by magnetic separation is more effective than that attained by gravity separation.Also,the latter method is more expensive and toxic. (5)The measured mechanical parameters,e.g. microhardness,strength,fracture toughness and density, show a sharp improvement in the quality of the product made of the processed granite relative to natural one. ACKNoWLEDGMENTS: The authors wish to thank Prof.Shi Cui.ze,the 地 质 与 资 源 2008芷 director of Laboratory Technology Center of China Medical University,Shenyang,and Prof.Han Yue—xin, exposure on the fracture toughness and flexure strength of a dental glass lJj.Dentalmateri'As,2001,(17):367—371. 16jChantikul P,Anstis G R,Lawn B R,Marshall D B.A critical evaluation of indentation techniques for measuring toughness:II.Strength method Pro£Quan Lian—xiang。Mr.Zhou Fei and Mr.Li Xian—xue from the Sch ool of Resource and Civil Engineering, j.JAmCeramSoc,1981,(64):539—43. 17 JSoumen Maity,Sarkr B K.Development of high—strength whiteware bodies lJ J.JEuroCeram Soc,1996,(16):1083—1088. Northeastern University,Shenyang,for providing the facilities to cartTout this work. [8]Evans A G,Wilshaw T R.Quasi—static solid particle damage in brittle REFERENCES: l 1]HU Bin.Features of Lixi granitic con@ex body and its genetic type discussion in South—Eastern Zhejiang Province,China[J].Zhejiang Geology,1997,(1):47—54. materials lJj.Acta Metall,1976,(24):939~940. [9]Mattyasovsky—Zolsnay L.Mechanical strength of porcelain[J].J Am Ceram Soc,1957,(40):299—306. 1 10]Winterling A Structure stress as the cause of increasing strength in porcelain lJ J.Bet Deut Keram Ges,1961,(38):9—22. 1 2 jGonzalez Besada D.Contribucion al estudio de la separacion de silicates de las rocas gallegas mediante floatacion monolaminar[D].Degree of licenciate thesis.Sciences Faculty.Santiago de Compostela University. 1984. Biography:MohamedEI-Omla(1967一),male,Egyptian, M.Sc.of Geology Department.Faculty of Science.Suez 1 3]Izquierdo Pazo M,Andrade Couce M L,Bao Iglesias M,Marcet Miramontes P.Obtention of feldspar raw material for porcelain and Canal University (1 997);PhD student of Geology ceramic industries from biotite—porphyrilfe granite(Porrino Granite). 1997. department,Northeastern University,China(2004). Contact address:Geology Department,Faculty of Science,Suez Canal University,Ismailia,PC 41522, [4]Dieter G E.Mechanical Metallurgy[M].3rd Ed.New York:McGraw— Hil1.1985.120. 15 JSusanne S S,Isabelle L D,Anselm H W,Urs C B.Effect of water Egypt.E.mail:elomella@hotmail.corn 陶瓷工业中对产白花岗岩的长石原料的提纯方法研究 Mohamed E1一Omla,Salah Shata (苏伊士运河大学理学院地质系,埃及伊斯梅利亚PC 41522) 摘 要:花岗岩是陶瓷工业中所需长石原料的重要来源之一.由于花岗岩中云母和氧化铁的存在,其最终产品的质量受 到影响(强度、硬度、密度降低).本研究对浙江花岗岩采用两阶段分离方法,以提高花岗岩中长石的质量第一阶段为重 力分离,去除重矿物杂质;第二阶段为磁性分离,进一步减少铁含量.用机械方法对不同加工阶段的3种样品进行了成分 .测试:1)原料花岗岩;2)第一阶段处理的花岗岩;3)第二阶段处理的花岗岩.结果显示,最终处理后的样品较之原始花岗 岩在显微硬度、强度、密度及裂隙坚韧性方面都有明显提高. 关键词:长石;花岗岩;重矿物;陶瓷工业;浙江省