 Hello, today we're going to talk about how we identify rocks and minerals and how we define them specifically and this is kind of like the strict Or fairly formal definitions of minerals and how that's different from rocks because a lot of times these two concepts are confused So we have rocks over here a beautiful granite and some nice And then over here we have some copper and quartz Topaz and these This copper and quartz and topaz all fall under the classification of minerals Whereas granite here and this nice are definitely rocks So how do we define a mineral and how do we define a rock and why should we know the difference? So here is the definition of a mineral and it varies a little bit from geologists to geologists, but based on the International mineralogical association a mineral must be naturally occurring Must be a solid at room temperature Must have an orderly crystalline structure defined orderly crystalline structure a Definite a well-defined chemical composition and It should be generally a biogenic meaning not made by life and these Number five is especially debatable by different geologists, but this is based on the IMA definition and Then number three is also or number two also comes under some debate as well as as does number three so we'll get into those Nuances a little bit when we talk in more detail a Rock is just a solid mass of minerals or mineral like matter that occurs naturally So that could just be a combination of different minerals or one mineral where it's not Well-defined, you know, there could be a number of impurities in that Rock that keep it from being officially just one individual mineral crystal So a mineral must be naturally occurring in a cubic zirconia because of that By definition is not a mineral because it's been man-made even though it shares a lot of the same Properties the definite chemical structure and the defined chemical composition the fact that it's a solid same for the methamphetamine featured in Breaking bad even though that has a definite chemical composition and a well an orderly crystal structure The fact that it is man-made Means that it is not a mineral and in terms of orderly crystal and structure What I mean is the atoms are arranged in a way and bonded in a way. That's well-defined and repeatable And and the best example I can think of here is glass versus quartz. They're both made up of silica dioxide But you can see here the arrangement of atoms in glass is much different than that Then the arrangement of atoms and quartz of course has this nice neat Framework Arrangement of silica tetrahedra. Whereas glass is kind of amorphous, right? And here are water molecules arranged very nicely in ice five And I kind of learned something new that ice has several different Crystal structures and so you have different numbers at following ice to accommodate for that How how can you tell if your mineral has an orderly crystal instruction a lot of times? It'll have natural flat sides And that could indicate both a crystal face or a cleavage plane and is some kind of repeating pattern in your crystal and Sometimes sharp edges and corners which kind of coincides with the the last two things definite composition that means that the mineral has The same kind of atoms in it every time and there's not like a big jumble of different atoms occurring in each one so quartz is always defined by silica and oxygen and calcite always has calcium and carbonate in it every time and That is its definite composition, but keep in mind that similar atoms can sometimes substitute for each other in in these Minerals for example, olivine can have magnesium and iron substitute for each other and Plagio clays can as well from sodium to calcium and then You can also have trace elements tiny amounts of other elements hanging out inside of the crystal structure and that can help Create different colors and tones and minerals as seen in these different quartz crystals here And then another thing to think about when it comes to composition is things can have the same composition But a different crystal structure, which makes them different minerals and that my favorite example is diamond and graphite diamond and graphite are both made exclusively of carbon, but They have very very different crystal structures graphite has this nice sheet like arrangement of carbon atoms and diamond has a More framework type arrangement of carbon atoms, so it causes for very different properties Of these two things and over here I have a man-made kind of arrangement of carbon atoms known as a bucky ball You know so I have carbon nanotubes and the graphene and all kinds of variations of arrangements of carbon atoms but Just keep in mind that you can have these poly morphs which are different arrangements the same type of atom Or the same types of materials and that concludes the discussion of The definition of a mineral Something worth noting is the generally a biogenic feature that is disputed among geologists some stricter definitions would exclude calcite made by coral and shells of other type of Organisms as not minerals and you have to wait until a geologic process comes into play before those can become minerals So it could be altered by Diagenesis, which we'll talk about later or something similar to that before you can get the calcite made by those organisms Becoming a mineral so just keep that in mind in terms of the definition and That concludes this lecture on the definition of a mineral. I hope you enjoyed it and we'll continue later