Mineral Identification

 Olivine is actually a name for a series between two ends members, fayalite and forsterite. Fayalite is the iron rich member with a pure formula of Fe2SiO4. Forsterite is the magnesium rich member with a pure formula of Mg2SiO4. The two minerals form a series where the iron and magnesium are substituted for each other without much effect on the crystal structure. Fayalite due to its iron content has a higher index of infraction, is heavier and has a darker color than forsterite. Olivine has many names besides its mineral names, Fayalite and forsterite. It’s also known as ‘Chrysolite”, “evening emerald” and Peridot. This mineral interests me because of its industrial uses as well as its characteristics. This mineral has been viewed by students in class.

Graphite is a polymorph of the element carbon. Diamond is another polymorph. These two share the same Chemistry, carbon but have very different structures and very different properties.

Diamond is the hardest mineral known to man; Graphite is one of the softest.

Diamond is an excellent electrical insulator; Graphite is a good conductor of electricity.

Somewhat of a surprise is that at surface temperatures and pressures, Graphite is the stable from Carbon. This mineral interests me because of its many uses by human and its similarities with Diamond. We have talked about Graphite in class and been able to see it. It can be found in most countries and one of its uses is pencil.  In fact, all diamonds at or near the surface of the Earth are currently undergoing a transformation into Graphite.