Mineral Identification

Friedrich Mohs wanted to figure out a way to identify minerals based on their ability to be scratched.  He chose nine common minerals (and diamonds) to create Mohs' Hardness Scale.  He gave each of them a number based how hard (easily scratched) they were compared to the others. 

#1 Talc can be scratched by the other 9 minerals in his scale. 
 #10 Diamond can not be scratched by any of the other nine.   

 He then carried these minerals with him in the field as tools to help him see how hard other minerals or rocks were.

Today, we did some testing of our own.  Using the property of hardness and some tools we took all nine minerals (the science lab can't afford diamonds...) and found out their hardness.  It was hard, but worth it!

This mineral (fluorite) scratches a penny and has a hardness of 4.

Everyone was able to identify these minerals using only the property of hardness!

See if you can use your knowledge to escape castle walls made from minerals using your knowledge of the hardness scale!  Notice the penny has the incorrect hardness on this scale, and we also learned that minerals of the same hardness don't scratch each other.  

http://www.fossweb.com/modules3-6/EarthMaterials/activities/mohsdrill.html

After we solved our hardness problem, we looked at other properties (in addition to hardness) such as color, cleavage, streak, luster, reaction to acid, and even whether the mineral is magnetic.

Mica breaks off in sheets.

Magnetite is magnetic!

Pyrite is gold, but leaves a greenish black streak.

Don't always believe that one type of mineral always looks the same.   Look at these samples.  All of them are calcite!

We can show these are calcite using hardness and reaction to vinegar.

For the academic in you, check out this slide show from Scholastic StudyJams.  Maybe even quiz yourself!

http://studyjams.scholastic.com/studyjams/jams/science/rocks-minerals-landforms/minerals.htm