Select either a MINERAL or a ROCK that has some economic value, practical use, or a harmful or beneficial effect. Create a discussion thread with the name of the mineral/rock as the title of the thread In your post, compose a paragraph or two and include the following:

The name of the rock or mineral.
A description of its chemical/mineralogical composition.
The geological conditions under which it forms.
Where it is found, and how it is collected.
A discussion of its economic value, practical use, harmful or beneficial effects.
Feel free to include an image of your rock/mineral (not required).
Include the NAMES and SOURCES of the materials you used to find the information you used in your post.