Hi.
Today we are going to melt some granite.
First, what we are going to do is we are going to light a methane-oxygen flame.
Methane is the same gas that you cook with at home if you have a gas stove.
There you can see the flame.
We are going to adjust it.
However, when you burn methane or natural gas at home in your stove, you burn it in air.
Here we're going to burn it in pure oxygen.
That gives us a little bit of a hotter flame.
Then, once the flame becomes properly adjusted,
we are going to hold a piece of granite
Let's see if we can see the granite at this point.
There it is.
It's a granite rectangle
being held, essentially, in a pair of needle-nose pliers.
And this granite, which is actually a type called granodiorite
will be placed in the flame and will start to heat up.
So we are adding heat to the granite
which will increase its temperature.
The flame is becoming very bright at this point.
And we should be able to reach a temperature close to 1500 degrees C
by holding this piece of granite in the flame.
1500 degrees C is the equivalent of about 2700 degrees Fahrenheit.
At these temperatures, the granite should melt completely.
In fact, some of the individual minerals,
such as magnetite that may be present in small amounts in the granite,
will probably melt nearly completely at this temperature.
Also, some of the minerals in the granite have water contained in their crystalline structures.
That water will form small bubbles in the molten rock.
When we're finally done melting a little bit of this granite,
the granite piece will be covered with what is essentially
volcanic glass.
And the glass could have small bubbles in it which will then be
representative of steam, the steam being produced by the destruction
of what we call the hydrous minerals
or the minerals that contain water in their structure.
One of the reasons that we are interested in molten rock
in this laboratory is that molten rock, of course, exists in nature.
Now, it's not heated by a flame inside the Earth,
rather the Earth even now is generating heat
by way of natural radioactivity
and in places the crust of the earth can melt.
There are many complicated processes
involved in the formation of a granite magma that I'm
glossing over at this point.
And the magmas can transport ore metals up toward the surface of the Earth.
Not to the surface, but near the surface,
the magma may cool in what we call a subvolcanic conduit
and release those ore metals into steam
that's forming bubbles within the magma,
that steam leaves the magma, can flow into fractured rock
and form veins of ore minerals and other minerals.
Essentially forming a mineral deposit
and that mineral deposit might be economic,
and if it's economic,
given the economic conditions and the technologies that exist
at any time, we might call it an ore deposit.
And an ore is something that can be mined at a profit.
So right now we are heating the sample up,
it's probably developing something of a molten rind on it now.
At some point soon we will remove the sample from the flame.
There you can see it glowing white hot still
Developing a little bit of a red edge as it cools
Now glowing orange, still emitting some radiation of it's own, electomagnetic radiation or light
Because it's hot now, it's probably just radiating in the infrared
We can't see any energy being emitted from the sample
And now the sample is just cooling because it's now in air
and the air is probably convecting
around that sample carrying heat away
and thereby causing the temperature to drop.
So here we see the result of the melting experiment.
This is a small piece of the granite which has melted.
You can see this glassy area on top of the specimen which is just a few millimeters across.
That is, for all intents and purposes, volcanic glass
that we created by melting the granite in the torch flame.
There are, if you look closely, some small spherical
structures that you can see within the glass,
one toward the upper center part of the glassy area
and that circular structure is in fact spherical
and is a bubble of steam,
and the steam was released from some of the
water-bearing minerals that were in the granite.
And so here, as you can see, we created volcanic glass
in the laboratory.