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Services & Methods
Whole Rock Quantification:The bulk sample is hand-crushed and divided as required for clay fraction analysis before grinding in a McCrone micronising mill. During grinding, the sample can be suspended in non-aqeous media as required, for example, when analysing evaporites or synthetic materials. The resulting powder is homogenised by hand grinding in an agate mortar before rear-packing into the mounting slide. Special mounts can be employed for small samples (down to 100mg) if required. Although the service is orientated towards geological samples, it is applicable to any crystalline material e.g. synthetic chemicals, scales or forensic samples. Typical sample size is >2g, although very small samples can be handled on special mounts for investigation. |
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Clay Fraction Quantification: Separating the <2 micron fraction is achieved by ultrasound, shaking and centrifugation. Size fractions other than <2 micron (e.g. 2-16 micron) are obtained by varying the centrifuge speed and time. The total weight of clay extracted is determined by removing a 20ml aliquot of the final clay suspension and evaporating to dryness at 80°C. The clay XRD mount is obtained by filtering the clay suspension through a Millipore glass micro-fibre filter and drying the filtrate on the filter paper. The samples are analysed as an air-dried preparation, after saturation with ethylene glycol vapour overnight and following heating at 380°C for 2 hours and 550°C for one hour. The initial scan for these four treatments is between 3° and 35° 2theta at a step size of 0.05°/sec. The untreated sample is then analysed again over the range 24-27° 2theta with a step size of 0.02°/2 sec to refine adjacent kaolinite and chlorite peaks. |
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X-ray Fluorescence (chemical) analysis: Major Elements: SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, BaO, P2O5, SO3 and Cl. Samples are first dried (105°C) then crushed and ball-milled (agate) to a fine powder and mixed with a fixed proportion of lithium metaborate (or a mix including tetraborate depending on the sample matrix). This mixture is then fused at 1080°C for 15 minutes and cast into a 32mm diameter glass "bead". Loss on ignition (LOI) is calculated on a separate portion of the powdered sample. Trace Elements: V, Cr, Co, Ni, Cu, Zn, Ga, Ge, Se, Br, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sn, Sb, I, Cs, Ba, La, Hf, Ta, W, Pb, Bi, Ce, Nd, Th, U. * Other elements may be possible depending upon the calibration of the measuring system. Approximately 10g of powdered sample is mixed with pva binder (Moviol) or wax and pressed at 20T using hardened steel anvils to produce a 32mm pressed powder pellet. The bead or pellet is measured using a Spectro X-Lab Energy Dispersive (polarised) XRF Spectrometer. The system is fully calibrated using international rock, soil, ore, sediment, ash, oil, plastics, and organic standards to ensure repeatable and accurate analysis. |
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Hot-shot and Fast-track Service: Any of the above services can be accelerated upon payment of an agreed surcharge (25-100%) depending upon the turnround required - applicable only to small batches of samples. |
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