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Rock star: Obsidian

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Did you know that most of the obsidian you see for sale is actually fake?  That’s the reason it has taken us so long to find some that we are willing to have in the shop.

Some of the newest rock money can buy, this obsidian is only 129 years old from the Mt Tarawera volcanic eruption in June 1886 in the Bay of Plenty Region, New Zealand.  Formed at the margins of rhyolitic flows it also contains pumice and perlite inclusions formed by contact with groundwater.

In the classroom, explore differences in structure compared to other rocks from felsic lava such as pumice.

Colour: black to black/green

Fracture: conchoidal

Mohs hardness :5-6

This obsidian has been collected for us by a geologist in New Zealand, so we will guarantee that it is the real deal and absolutely not fake so it has the Angus Seal of Approval

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The Western Victorian Volcanic Plains (or Newer Volcanic Province) Part 2

The Hound headed west from Sunbury and passed a memorial to Harry Houdini (near Plumpton), who conducted the first powered flight in Australia (a bit more about links to Harry later). After driving several hours more in the rain, we were in Hamilton and lodged at Murroa Station near the western limit of the plains and overlooked by Mt Napier which was the site of the most recent eruption some 7200 years ago. This is so recent that the sound it made-Murroa- has been passed down in local aboriginal spoken history, hence the name of the station.

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Mt Napier (M. Rowe)

One of the hounds (Skip) at Murroa and his master took us to see the scoria flow off Mt Napier. Now Skip has a special talent, apart from being a great sheep dog, he can slip his collar, no matter how tight it is. A bit of a Houdini character if you ask this Hound.

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Scoria flow to the right (west) from Mt Napier

In Part 3, The Hound heads back east to Organ Pipes National Park (but they wouldn’t let him in because he’s a dog).

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The Western Victorian Volcanic Plains (or Newer Volcanic Province) Part 1

On a recent trip through Western Victoria, the Hound spotted some magnificent colonial architecture in Sunbury (about 45 minutes NW of Melbourne) constructed of the local bluestone (basalt) which peaked his interest about where all this rock was coming from. There were many basalt quarries around Sunbury which supplied stone for local works and for many significant buildings in Melbourne. The local tourist guide has several walking and driving tours to take in the sights, one of which is the magnificent arched bridge over Jackson Ck which you see driving into town from Melbourne. Many of the basalt blocks in this bridge have vesicles within which quartz crystals have grown.

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Vesicles containing quartz in basalt.

In Part 2, The Hound heads west from Sunbury.