harryopal
I wonder if there are any geologist followers of this website? The reason I ask relates to a post i just made on an an Australian fossicking webdsite remarking on the lovely specimen volcanic, olivine bombs sprinkled with peridot that used to be found (maybe still found) at a place called Mt Shadwell in Victoria.
Mt Agung keeps venting every now and then which makes me wonder if it is reasonable to suppose that one might find similar volcanic, olivine bombs around the flanks of Mt Agung? Are olivine bombs a feature of all erupting volcanoes or does it require a particular type of geological formation.?
spicyayam
If you are on Facebook, try asking Peter:
https://www.facebook.com/peter.rendezvous.9 He seems quite knowledgeable.
harryopal
Thanks, Spicyayam, I followed up as suggested and had this reply; ".... you'd have greater success looking in hawaii .. there is no olavine bombs as you call them at Agung. Olivine is made up primarily of magnesium, iron, silicon, and oxygen, and the combination of the latter three creates a class of mineral known as an iron silicate. It doesn't come raining from the sky or eruptions.... it can be found in old lava having formed after ejection. "
mugwump
Hi Harry,
I have an inquiry perhaps you can answer. West Bali has a number of black sand beaches which seem to be the object of diggers apparently transporting the sand because of some commercial value. This product can't be practical in construction projects because it also contains salt which dissolves as it dries. So what mineral ingredient could possibly be contained to make it commercially desirable?
Peter apparently has a restriction on his account precluding his availability.
harryopal
Good morning Mugwump,
It seems the more I know, the less I know so I don't pretend to have any expertise in geology or just about anything. Black sands may contain magnetite and rare earth elements as well as sapphire, topaz, ruby and garnet. I am unaware of any commercial mining here for those elements but I am not familiar with what is being done in west Bali. Nor am I a builder but because the black sand is composed of larger granuals than the finer white sand it may lend itself to being a better mix for making concrete. Then I may be wrong on every count. Sorry, I can't be more authoritative.
mugwump
Appreciate your response. Yeah, it's been a puzzle to me because black sand from fresh water is used in cement, but the beach material loses it's bonding qualities in cement as I know from experience. Thus it must comprise some element of value in another use, and is rumored to being exported.
