Question about olivine?

Question

When Olivine is found in nature is it usually found as a mixture of its two end members?

Answer 1

No. To find pure foresterite (magnesium olivine) or pure fayallite (iron olivine) is rare. Usually olivine is zoned, meaning the foresterite to fayallite content changes from the core to the rim of minerals. That is due to the fact that foresterite solidifies at higher temperatures than does fayallite. It is possible that the rims of olivine crystals are almost pure fayallite.

Answer 2

Pure Forsterite and Fayolite are rare, so it's usually expressed in % of Forsterite, equal to percent of Mg in relation to total of Mg/Fe. So if there is 1 Mg for every 3 Fe, you've got a 25% Mg Olivine, so a 25% Forsterite.

So yes, it's almost always a mixture of the two end members.

Answer 3

What the guys said above is true...it is always a mixture of the two end-members, forsterite (Mg) and fayalite (Fe). Pure fayalite is not found on earth, and (I am pretty sure) that as close as one gets to pure forsterite is something like San Carlos olivine, which is 98% forsterite and 2% fayalite.

Answer 4

The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. It is one of the most common minerals on Earth, and has also been identified on the Moon, Mars, and comet Wild 2.
Oh, and, i dont get what your question is, but this is what olivine is.