"There are 4 things that must be satisfied for a substance to be a mineral:
(i) natural
(ii) inorganic
(iii) solid in crystalline form
(iv) definite chemical composition"

I don't fully understand (iii) and (iv).

1) Gold is a naturally occurring inorganic substance that forms in the earth's crust. It is a solid and has a definite chemical composition. Is gold a mineral? Explain your answer. (Assume you know nothing about gold, as if it is an unknown substance that you have to determine if it is a mineral or not.) This is a question from my text book's section review.

From the above information, gold seems to be missing something that must be satisfied to be a mineral, gold is a solid but is not mentioned to have crystalline form. For a mineral layman like me, I would predict that gold is not a mineral according to the information provided, right?

For (iii) solid in crystalline form, is it true that a solid always has crystalline form, and a substance that has crystalline form is always a solid? If so, I would predict that gold is a mineral now since the information says that it is a solid, and this automatically satisfies the (iii) requirement. If not, gold is not a mineral...I think...

2) For the (iv) requirement for a mineral, "definite chemical composition", what does it mean by that? I don't get it! Is concrete a mineral and why?

3) Are rocks mixtures (not chemically united) or compounds (chemically united)?

4) An example of a mineral with a basic structure consisting of single tetrahedra linked by atoms of other elements is ________
(pick one of mica, olivine, quartz, or feldaspar)
I can't tell if the answer is mica or olivine, can someone explain?

I don't understand! Can someone who know "minerals" explain? Thanks a lot! :)

anybody home? :eek:

1) Gold does qualify as a mineral. All metals have some sort of a microscopic crystalline structure, even though it seems non-brittle. And yes, it has a definite chemical composition because it is an element. I'm not too sure, but I think gold has a face-centered cubic crystal structure (like Pb). Meaning that gold crystals are possible to grow from vapor condensation.

2) By "definite" they mean you can describe the entire mass as a homogenous piece of (insert chemical formula here).

This would mean that concrete is not a mineral. Concrete is a composite material (from gravel and cement, where the gravel may have many compositions).

3)I'll let you answer this one for yourself.

4)"Single tetrahedra" is a misnomer. And thus, I don't really get what it's trying to ask.