Determination of low levels of quartz in calcium carbonates by x-ray diffractometry

✍ Scribed by N.J. Elton; P.D. Salt

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 898 KB
• Volume: 286
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)80176-2

✦ Synopsis

Naturally occurring calcium carbonates often have a complex accessory mineralogy. Quartz is a common associate, typically present at concentrations < 1 wt.%. A method is described whereby x-ray powder diffractometry may be used to quantify quartz in such samples to better than f 0.01 wt.% (la error) at the 0.1 wt.% level. The quarts in the samples is pre-concentrated by partial acid dissolution of the calcium carbonate, and careful attention is given to reproducible sample preparation of the resultant partial residues. Calibration is by an external standard with mass absorption corrections being applied to compensate for variations in sample chemistry. The presence of additional accessory minerals such as mica and feldspar can lead to problems due to overlapping diffraction peaks. These problems are discussed and the use and limitations of the short range profile fitting techniques employed in this method are described. The significance of particle statistics, counting statistics, and the variability associated with sample preparation in limiting the accuracy of quantification at low levels is also examined.