I
think the images say enough. The rather large 30cm Fresnel lens
was scavanged from a discarded overhead projector. The rock is common
slate. This rock is fossilized ooze from the floor of a long
forgotten ocean . It appears not to contain fossils of anything
interesting. It was necessary to view the focused sun spot with
arc welding googles. You can notice that alongside the moltern
zone, iron oxide in the rock has been baked ,the Fe203
oxide giving it a distinctly red coloration. This slate rock has
a lower fusion temperature than say granite, because of its high
lime content. This lens cannot fuse quartz or more
reflective material. Monumental lithography is a possible
use of this idea?
When viewed with welders googles, the
molten rock bubbles as entrapped gas is forced out. The rock reaches
bright yellow heat at the lens' focus. This experiment
was done during a bright day in Melbourne at about local midday.
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