Mineral Set 1 Questions

Question 1

At normal surface conditions quartz exists as low quartz which belongs to the trigonal crystal system. Why does it sometimes show hexagonal symmetry?

Answer 1

High temp quartz has a hexagonal symmetry, but once it cool, it shows trigonal. However, the external shape of the crystal remains hexagonal, but the internal structure changes to trigonal.

Question 2

In what environments are Tridymite and Christobalite formed? What kind of trasnfomration must occur?

Answer 2

low P, high Temp. environments. Transformation to low quartz requires Reconstructive transformation.

Question 3

What is jasper and in what ways does it differ from chalcedony?

Answer 3

Jasper is red, jasper is granular (Chalcedony is fibrous), Jasper has impurities such as Hematite.

Question 4

Tiger eye is quartz that is replaced by another mineral. what is that mineral?

Answer 4

Crocidolite (an Amphibole).

Question 4

Opal is a hydrated form of Silica. It contains water in it’s structure and Opal is softer than Agate.

Question 5

Perthitite (K-spar with perthitic texture) is a banded segragation of two minerals. What are the minerals?

Answer 5

K-Feldsapr and Na-Rich Plagioclase.