pumice - teaching student specimens - glassy dark gray - UNIT OF 5 SPECIMENS

Description

If making multiple purchases, please read the note following the
red text
below!
Pumice -  teaching student specimens of glassy dark gray to black pumice  -  UNIT OF 5 SPECIMENS
Forcefully ejected from a volcanic vent, pumice hardens as it flies through the air, trapping bubbles of gas. It is light enough to float on water - these specimens will all float. The composition of this silica rich volcanic rock is similar to that of obsidian or granite. The silica poor equivalent is scoria or volcanic cinder. Also full of entrapped gas bubbles, scoria's composition is the same as basalt, the lava that makes up the Hawaiian and other island chains as well as the oceanic crust.
Cinder cone volcanoes composed of pumice are not common. Silica-rich glassy lava is sticky and eruptions tend to be explosive, causing wide distribution of the pumice. After the eruption of Krakatoa, the sea was coated with floating pumice for miles around.
Scoria and basalt are silica poor, so lava readily fountains from vents. Loose pieces of scoria form any number of small cinder cone volcanoes in the western U.S. Both pumice and scoria are mined as decorative rock. Students will recognize scoria as "McDonald's flower bed rock." Pumice is used as an abrasive.
Not all pumice will float. The large holes in this pumice fill with water almost instantly and it sinks. This pumice comes from Mono Craters, a row of small silica-rich cinder cones in Mono County, California. The field photo shows one of these cones.
We really don't like the tiny finger nail-sized specimens offered to students, as we feel these are too small to see rock textures and too small for examining the identifying characteristics of a mineral. We want the "Oh, Wow!" effect when students see the set of specimens they are going to work with. We collect these specimens so that five specimens, or possibly six, will fit in a small flat rate box, and we keep the price low, as we know these will be used in a classroom. For teachers we count like a baker and a dozen is more than 12, since you will always need a few spares.  If you are a teacher, let us know.
Making multiple purchases?
Just add items to your cart. When finished shopping, click on
“request total”
at upper right in the Shopping Cart window.
Do not proceed to checkout.
We will send an eBay invoice with the correct combined shipping.
The combined shipping will often be less than eBay shows. Please wait for that invoice before paying.
There is no obligation to purchase. You can decide after seeing what shipping will cost.
Shipping:
By first class mail unless combined with other purchases
International customers:
We sell and ship internationally. If eBay’s page does not let you enter your country name to determine the shipping cost for something you are interested in, please contact us.  We can tell you what the shipping would cost and how to make the purchase. You can then decide if you wish to complete the transaction. Use the
Contact Seller
link in the Seller Information box on the right side of this page.
Pay securely with your debit or credit card through PayPal! You do not need a Pay Pal account to do this. Yes, we do combine shipping!