Rocks and Minerals Question Marathon

[wufactor2012]

you are right! but what do you when they don't have any other colors on it

[sofossils]

Is it....[hide]The right one is goethite, the left one is hematite. Hematite has a crystal structure that is trigonal/hexagonal, while goethite has a orthorombic crystal structure. Hematite may also include red, while goethite won't. Hematite has more specific gravity, and a darker streak. [/hide]

[eox]

streak would be the way to go for me, if there wasn't any color.
should i post the next question?

[wufactor2012]

yes you can go, but usually in competitions we are not allowed to use streak plates

[aim4me26]

we are not allowed to use streak plates

...Are you sure?

I'm pretty sure at the competitions last year, my partner and I, as well as the rest of the teams, were allowed to use them. They were provided at almost every station.

[sofossils]

Every state varies, I've had them, and I'm from PA.

[melissay63]

its only if they provide it...its not as if you can take it with you and put it in your sheet protectors. I saw some teams do that for my regionals

[eox]

it varies by the rules, but streak plates are usually allowed.
ID both and tell how you could differentiate. also describe the formation.

HERE! (Click to Show Hidden Text)

[img]http://tinyurl.com/akecyxz[/img]
[img]http://tinyurl.com/aaun2ez[/img]

[zimmy1235]

Answer (Click to Show Hidden Text)

The top one is a barite rose and the bottom one is a gypsum rose. I could tell by the much more defined and sharp edges on the gypsum rose, though a giveaway sign is weight because barite has a much higher specific gravity than gypsum. These rose crystals form when sand is trapped inside the crystals when they are forming.

[sofossils]

[hide]The first one is barite, the second one is selenite gypsum. Barite is harder, and MUCH heavier. The formation that both are in is commonly called desert rose; sand is very common to be found in specimens. [/hide]