Honored Contributor
Posts: 9,471
Registered: ‎03-13-2010

My Volcanic Rocks

[ Edited ]

Here are a few rocks I kept from the large collection I had when I was teaching. These are all volcanic rocks. They’re not always as pretty as crystals & minerals, but I still think they are interesting. 


The large grey rock is pumice from Mt. Pinatubo in the Philippines. Pumice forms when lava with a high water & gas content cools & hardens resulting in its porous nature which is why it is such a lightweight rock. I had a student in the 1990s whose grandparents lived in the Philippines, and he brought this back to me as a gift. 


The black rock is obsidian. Obsidian is a type of volcanic glass formed from cooled lava that contains high amounts of silica. The reddish rock is granite. Granite forms from the crystallization of magma beneath Earth’s surface. 








Respected Contributor
Posts: 4,445
Registered: ‎05-15-2014

@wilma   I love this stuff, thank you again for posting.  I loved your rock and mineral pictures the other day too!   I have a very small piece of rock (greenish) from the Mt. St. Helens eruption.  I bought it in the visitor center so I'm assuming (hoping) it's authentic.

Esteemed Contributor
Posts: 5,521
Registered: ‎03-30-2014

Thanks for such nice pics.  Got to say today's lack the prior beauty.


After Krakatoa the floating the lava damaged hulls and disrupted shipping for a long time.  Hard to imagine.  Would have been something to see.

Respected Contributor
Posts: 3,533
Registered: ‎03-19-2016

@wilma  Interesting!  My son and I were on a tour in Hawaii. We toured the volcanic sites and several of us picked up a piece. 
  Returning to the bus our guide explained the bad luck people have had because of taking the rocks. He said some have even mailed them back. 
  We all left our rocks there!🌋

Trusted Contributor
Posts: 1,811
Registered: ‎11-24-2011

@wilma  Very interesting and cool !!!!