Preliminary: Rocks and Minerals

[Luo]

do you guys know of any other mineraloids?

There's a very convenient list on Wikipedia.

[Cheesy Pie]

I can't trust that list. Mixtures of minerals are ROCKS, not mineraloids. Sorry Luo.

[Luo]

I can't trust that list. Mixtures of minerals are ROCKS, not mineraloids. Sorry Luo.

Which specific items on that list do you believe to be erroneous? The classification of Lapis Lazuli as a mineraloid seems somewhat questionable, but other than that, I don't think there's much reason to object to that list.

EDIT: Alternatively, you can check out a shorter list here.

[yogoperson]

I can't trust that list. Mixtures of minerals are ROCKS, not mineraloids. Sorry Luo.

Which specific items on that list do you believe to be erroneous? The classification of Lapis Lazuli as a mineraloid seems somewhat questionable, but other than that, I don't think there's much reason to object to that list.

EDIT: Alternatively, you can check out a shorter list here.

It's just Wikipedia can be edited, and sometimes people add wrong info in there, that's all.

[gneissisnice]

I can't trust that list. Mixtures of minerals are ROCKS, not mineraloids. Sorry Luo.

Incorrect. They still need a crystal structure, even to be a rock (in that case, every mineral would have to be a crystal, so while the entire rock doesn't have a repeating crystal lattice, every individual crystal does). So like I said, obsidian may be a mixture of minerals, but it's more correctly a mineraloid than a rock.

[anatomy]

true
but is that list actually accurate?

[sparky007]

Does anyone have the 6 Box Rock and Mineral Set? I bought it way long ago and now I'm competing in it again this upcoming year.. Soo if you do have that set, does anyone have the key to it??? If time permits could they type up what it was? I know this is a lofty request, and I'd be eternally indebted to someone!

[sparky007]

ALSO!
What's the difference between Cleavage and Fracture!?! I have NO idea!

[gneissisnice]

ALSO!
What's the difference between Cleavage and Fracture!?! I have NO idea!

They're both ways that a mineral breaks, but the difference is that cleavage is a breakage in one or more directions causing a smooth surface while fracture has no pattern, it's much more rough.

Cleavage has to do with the internal arrangement of atoms. In many minerals, there are planes where the bonds between atoms are weak, and so they prefer to break along those weaker planes. An example of that would be mica. Mica has a perfect basal cleavage; it's well known for easily breaking into sheets.

Fracture occurs when the mineral is forced to break in a direction that doesn't have a cleavage plane (and some minerals don't have a cleavage plane at all). Quartz only exhibits fracture; specifically, quartz has conchoidal fracture, so when it breaks, it forms smooth curves.

So if you see a flat smooth side, it's caused by cleavage. If you see a rough side, or a smooth curve, it's fracture.

[rivaroxx]

Does anyone know some good college textbooks to study for this event in Division C?