Geoscience Reference
In-Depth Information
a lapping machine (
15
) using carborundum or aluminium
oxide abrasive power with a minimum particle size of
5 μm (F1000 grade).
Highly polished specimens differ from finely ground
slices in that a finer surface finish is produced, and as
this is difficult to achieve over a large area, the specimens
are much smaller (typically <30 mm diameter round
blocks). Samples for high-polishing are oven-dried and
encapsulated in resin using a round mould. Once the
resin has set the specimen is removed from the mould,
roughly ground flat using a diamond cup wheel, and
then polished using a polishing machine (
18
).
16
16
Thin sections in three different sizes; small (left), medium
(middle), and large (right).
17
18
17
Microscopical view of an air void in mortar, seen
in thin section. The void is lined by resin used to
consolidate the sample (dark green) and the void
centre is filled by epoxy resin used to set the glass
cover slip. The glue exhibits first-order interference
colours; XPT, ×150.
18
A polishing machine for making highly polished
specimens or polished thin sections. (Courtesy of
Logitech Materials Technologists and Engineers.)
