Sample Requirements

Please read the information on Tephra Sample Preparation Procedures (PDF) and the information on epoxy resins found on the SIMS page.

• For quantitative analysis the specimens must be flat, well polished and as free from surface voids as possible.

  Final polishing should use 0.25 micron abrasive
  Samples with porosity should be vacuum-impregnated with resin to fill void space

• Samples must be cohesive, so as not to shed particles whilst in the SX100
• Samples must be in a format compatible with the SX100 sample holders. Permitted formats are:

Thin sections: 45-48mm long, up to 25mm wide, 1mm thick with up to 0.5mm thick polished sample above the glass slide
Disks: 25.5mm or 29.5mm diameter, thickness 5-30mm
It may be possible to accommodate other formats - please discuss details with Chris Hayward
Lakeside, Canada Balsam and styrene-based resins must not be used for preparation.

• Samples need to be coated prior to analysis with a thin film of carbon. This is done at Edinburgh.

Samples should arrive at the laboratory 2 days before the EPMA session for coating
Samples must be cleaned after polishing to remove abrasive particles and lubricants. This can be done at Edinburgh if necessary.
Other coating materials such as gold can be used if required, but please discuss this as far in advance of making a booking as possible.

Facilities exist at Edinburgh for users to prepare certain types of sample prior to EPMA analysis - please contact Chris Hayward to information.

Please discuss any queries related to sample preparation or format with Chris Hayward well in advance of your scheduled EPMA booking

Following acid digestion of the original core sample (Dugmore et al., 1992, Pilcher and Hall, 1992, and Hall et al., 1994), the remaining mineralogical portion is embedded in epoxy resin. The sample is initially ground on progressively finer carborundum grit papers and then polished with 6 and finally 1 micron grade diamond pastes. Preparation techniques depend on the both the size of the individual tephra and the quantity of material available. The details of the acid digestion procedure may be found at Tephrabase. When analysing microtephras and a high proportion of mineral or biogenic silica matter is present, it may be necessary to use other methods, such as heavy liquid separation to isolate and concentrate the glass shards for analysis.

Potential users are strongly encouraged to discuss the sample preparation with a member of the Staff prior to arrival. Grinding, polishing and carbon coating facilities are available within the Tephrochronological Analytical Unit. For analytical reasons, we strongly advice clients to have their samples for electron probe microanalysis carbon coated within in the Unit.