Routine instrumental procedures to characterise the mineralogy of modern and ancient silica sinters
✍ Scribed by N.Rina Herdianita; Kerry A. Rodgers; Patrick R.L. Browne
- Book ID
- 104333462
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 315 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0375-6505
No coin nor oath required. For personal study only.
✦ Synopsis
Tightly constrained determinative methods can be used to characterise the silica minerals (opal-A, opal-CT, opal-C, quartz, moganite) and physical properties of silica sinters. Optimal X-ray powder diraction operating parameters indicate silica lattice order/disorder using untreated, dry, <106 mm powders scanned at 0.68 2y/min with a step size of 0.018 from 10±408 2y and an internal Si standard. Simultaneous dierential thermal and thermogravimetric analysis of 15.0 2 0.1 mg sinter samples of <106 mm grain size, at a heating rate of 208C/min in dry air, identify thermal events associated with dehydration, organic combustion, and changes of state. Where abundant organic matter is present, nitrogen is the preferred atmosphere for thermal analysis. Thermogravimetric-determined water contents of sinters dier from Pen®eld determinations re¯ecting the diering nature of the two techniques. Laser Raman microprobe techniques can be used to explore the mineralogy of particular sinter morphologies and habits down to 10 mm diameter. The nature of the silica species present can assist in characterising individual sinter deposits and, combined with textural, density and/or porosity determinations, can lead to a better