Please click on photo for enlargement
Dimensions: 117.1 x 77.6 x 49.0 mm max.
Name: Olivine Bomb
Location: Mortlake, Victoria, 380330S 142900E,
Date: Find: October, 2008
Weight: 566.0 g
The cut surface of this specimen are fine sanded and polishedl..
This 'meteorwrong' is from the depth of our earth, thrown out at a volcanic eruption as a volcanic or olivine bomb. This is as close as we can get to samples from the core of our Earth, unveiling the secrets of our planets build-up.
It is filled nearly completely with nice green olivine crystals, most of them shattered by the enormous forces of the eruption. It has been cut to show the interesting interior. The piece has a very nice lava/ scoria crust.
Mount Shadwell is the highest of a group of scoria cones overlaying a small accumulation of tuff and surrounded by lava flows. The arrangement of four overlapping scoria mounts suggests an original crater with a high southern rim opening towards the nothwest, but largely covered by later eruptions. It is assumed that this happened within the last million of years. The scoria comes from beneath the earths crust, approx. 250 km below, and is ejected as particles ranging in ash ( up to 4mm), lapilli (4 - 32 mm) abd finally blocks and bombs ( ranging from 32 mm upwards). The bombs are often drop shaped due to their solidifying from a liquid or semi liquid form as the plummet through the air. Mt. Shadwell is noted as a good source of olivine and augite ultramafic xenolith as well as clinopyroxene and orthoclase megacrysts contained in basalts and scoria. The host rock is basanite which is the most common lava of the explosive centres.
This is a Specimen not to be missed in a Meteorite or Mineral Collection, but it is also quite a show piece on it's own.