Identifying mineral composition
Some minerals fuse under the fire as easily as wax, while others may not be able to be fusable at all. Know that the blowpipe reaches max temperatures of around 1500 celcius near the oxidizing area of the flame. Below is the scale of fusibility that scientists have devised to differentiate how fusable some minerals is compared to others.
The way in which your mineral reacts to the heat, also is a measurable quality. For instance besides melting the blow pipe might cause it to... Swell up, throw out little globules (as in stilbite)
Intumesce, bubble up then fuse (as in scapolite)
Exfoliate, swell up and open out in leaves (as in apphyllit)
Glow brightly, without melting (as in calcite)
Decrepitate, break violently into fragments (as in barite)
So while checking for how well it fuses, keep an eye out for identifying its fusing effects as well.
If you were to chip off a piece of your mineral and hold it over a bunsen burner, you will see that the color of the flame will change according to composition. For instance Strontium produces a reddish flame, and barium produces a green flame
The position at which you choose to hold your mineral at the blow pipe will dramaticly change the result
of your experiment. For example the oxidizing flame (on the left) will actually add oxygen to your mineral!
For instance manganese, MnO, will change into a higher oxide of Mn2O3 using the oxidizing flame.
The reducing flame (on the right), however, will reduce the oxygen composition in your mineral. For example
ferric oxide, Fe2O3, will change into ferreos oxide, FeO, when put under the reducing area of the flame.
But how does the area at wich you hold the mineral In the flame effect the mineral differently!?
The mineral under the oxidizing tip of the flame is subject to oxygen that imparts oxygen into its composition.
However the mineral under the reducing flame has absolutely no oxygen surrounding it, and therefor loses its
own oxygen instead. (Note that oxygen is flamable.)
|Open tube testing|
|Closed tube testing|
|When making an open tube test you need to have a glass tube that's 12 centimeters long, and 4 millimeters in diameter with both sides not capped. Place your powdered mineral inside about... 2.5 centimeters from an end. Hold the tube at an angle as vertical as possible (45 degrees is recommended). On the opposite side of the mineral, heat so that the air is inclined to go upward. After this, move the bunsen burner under the mineral and allow the process of oxidization to take place. Oxygen inside the mineral form on the sides, or escape as gasses. What is left is the elements you need to make a further added test. Open tube testing is not very well recommended unless you are testing for sulfer, SO2. In that case the oxigen will leave, and a stinky smell will speak of victory to your inhaling nose.|
|Closed tube tests are similar to open tube tests. Simply place your mineral inside a cylindar if 8 centimeters in length, and 3-5 millimeters in diameter with only one capped side. From what I've learned the angle of the closed tube test should probably be near vertical and placed over a bunsen burner. Make sure you place Place your powdered mineral in the closed end part of the tube.The result will probably leave you to deal with just the mineral's elements. The color of the coating along the sides of the tube will give you a good idea of what they are, and extra characteristics such as droplets of water, or yellow when cold will aid you even more.|