P AGE 28 XRD XRay Diffraction Mineralogy by Powder Xray Diffraction XRD Major Phases Present Powder Xray dif fraction is one of the most powerful techniques for the identification of minerals in geological and i n d u s t r i a l sa mp l e s a n d t h e t e c h n i q u e o f c h o i c e f or W h o l e r o c k m i n e r a l i d e n ti f i c a t i o n C l a y s p e c i at i o n I d e n t i f i c a t i o n of crystalline forms of silica Alpha Quartz and Cristobalite Mineral Identification Most Minerals are crystalline and therefore scatter Xrays in a regular characteristic way dependant on their crystal structure Each mineral produces a unique dif fraction pattern and can be recognized from that pattern like a fingerprint Identification of minerals is made by comparing their dif fraction patterns with a library of over 17000 mineral patterns stored in the International Centre for Dif fraction Data ICDD Detection limits depend on the sample For geological material it is estimated that the minerals present in less than 3 of t he sample might not be detected The samples for Xray dif fraction analysis are ground or milled to a fine powder and then hand pressed into the sample holder Approximately 1 cm 3 of the material is suf ficient for rock mineral analysis but smaller amounts can also be accommodated by using a low background holder Clay Speciation Xray dif fraction combined with dedicated sample preparation is the most ef fective technique for precise identification of cl ay minerals The amount of sample required for clay speciation depends on the amount of clay fraction present Since several oriented mounts have to be p repared the required amount of sample is typically 10 15 g or more Unprepared samples are required Alpha Quartz The quantification of crystalline silica phases Alpha Quartz in bulk samples is carried out as an extension of the usual quan titative XRD procedures absorption correction internalexternal standard methods and whole pattern analysis depending on the sample Several grams of sample are required In cases where industrial applications may cause silica to become airborne the samples are collected and analyzed on filter me mbranes following the guidelines of NIOSH 7500 or OSHA ID142 Methods for respirable Alpha Quartz Determination of concentration of amorphous silica is performed following NIOSH Method 7501 The method uses the property that most amorphous forms of silica transform to cristobalite with heat treatment at 1 100C or 1500C After firing the sample is analyzed for cr istobalite following steps similar to Method 7500 Cluster Analysis At Actlabs we determine the XRD spectrum and use this statistical tool that groups XRD patterns into clusters based on the similarity of their peak and profile information It can be u s e d t o r ap i dl y g r o u p l a r g e d a t a s e t s i n t o s m a l l e r c l u s t e rs w i t h m o r e s i m i l a r m in e r a l o g y Selected samples in the cluster can have Rietveld quantitative determinations made This has potential applications for mining and exploration wherein clustering would highlight existing changes in mineralogy within a deposit Clustering would also be useful for deter mining mineralogical variability which may have metallurgical implications Code 9 Price Mineral Identification semiquantitative minerals are identified and their amounts determined using the Rietveld method 100 00 Mineral Identification quantitative minerals are identified and their amounts determined using the Rietveld method 15500 Corundum is added to the sample as an internal standard in order to determine the amount of Xray amorphous material Mineral Identification qualitative minerals are identified however their amounts are not determined 7500 Clay Speciation 30000 Alpha Quartz 10000 Mineral Identification Rietveld Clay Speciation 40000 Cluster Analysis applicable only to high volume applications on request Quantity discounts may be applicable Determination of samples which have similar XRD patterns but indistinguishable by the naked eye can identify where you are in a n alteration system as well as identify metallurgically dif ficult samples for processing due to changes in mineralogy Using quantitative XRD andor QEMSCAN or MLA can determine what these dif ferences are 3D Principle Component Plot