Rocks and Minerals Question Marathon

[iYOA]

Question 7 Answer (Click to Show Hidden Text)

This is Amazonite(microcline).  One big giveaway is the color, as well as the perfect cleavage and distinctive crystal pattern.

For all id, I think we should also provide reasoning as to why we made that choice so it can be more helpful to people reviewing these questions.

[quizbowl]

Question 7 Answer (Click to Show Hidden Text)

This is Amazonite(microcline).  One big giveaway is the color, as well as the perfect cleavage and distinctive crystal pattern.

For all id, I think we should also provide reasoning as to why we made that choice so it can be more helpful to people reviewing these questions.

Good job! And that's a great idea, by the way

[iYOA]

Question 8 (Click to Show Hidden Text)

[img]http://www.earthlightgems.com/sitebuildercontent/sitebuilderpictures/castletipselenite.JPG[/img]
[img]http://www.mythnlynx.com/images/selenite1.jpg[/img]
[img]http://www.crystalstargazer.com/seleniteSphere80mm4.0.JPG[/img]

a) Identify it.
b) In the last picture, what optical property is illustrated by the band of light which runs across the specimen.

[XXGeneration]

Question 8 Answer (Click to Show Hidden Text)

a) Identify it. 
Selenite [Gypsum]
What tipped me off was luster and transparency; it's like sort of glossy, but not really... dunno how to explain :P

b) In the last picture, what optical property is illustrated by the band of light which runs across the specimen.
Cat's Eye

[iYOA]

a is correct, b is very close; i think the formal term for it is chatoyancy.

[XXGeneration]

a is correct, b is very close; i think the formal term for it is chatoyancy.

"The term Cat's Eye, when used by itself as the name of a gemstone, can only be used to refer to a Cat's Eye Chrysoberyl. Any other stone exhibiting this phenomenon must have the stone's name after the Cat's Eye identifier, e.g., Cat's Eye Aquamarine."

This was on the wikipedia page for chatoyancy; cat's eye redirected there. Hopefully testwriters won't be that picky!

[iYOA]

yep lol.

ur turn

[XXGeneration]

Question 9? (Click to Show Hidden Text)

[img]http://www.irocks.com/db_pics/mdpics/MD-224741a.jpg[/img]
1. What is the mineral? 
2. Name the group that this mineral belongs to.

[XXGeneration]

If no one answers in the next 24 hours I will most likely give the answer in order to keep this thread from dying :3

[rocketman1555]

In order to keep this thread alive here is a new question.

What type of rock makes up Mammoth Caves?

What is its chemical composition?