[Music] [Music] hey there the goal of this video is to explore the different physical characteristics that minerals display as well as how we can use those characteristics for identification purposes so let's dive right in the characteristics we're gonna look at include color streak luster breakage hardness as well as a handful of other characteristics so let's begin by looking at color so when we're talking about color what we're talking about is the visible color that a mineral appears to the naked eye so what do you see when you actually look at the sample now it's important to note that color is generally not a reliable characteristic to use for identification so let's see why it's really not the best thing to use if you look at these two mineral samples they look very similar in fact their colors are almost identical purples but the fact is the one on the left is quartz and on the right is fluorite and so if we see multiple minerals appearing in the same color then color might not be the best characteristic to use for identification just to drive this home take a look at these two samples also look very similar in this kind of milky white translucent color the one left is calcite and the one on the right is halite so again color not so great just one more quick example here are two minerals that both have a very metallic silver looking color the one on the left is magnetite and on the right is Galena so you can see color does pose some challenges and in fact it it poses some additional challenges take a look at all of these mineral samples the fact is they're all quartz so quartz exists in multiple colors and so because of these issues color is not a reliable characteristic to use for identification that being said we do use it as a starting point sometimes but we don't really rely on it by itself and so we have to turn to some other physical characteristics to help us another example of a characteristic that we can use is called streak so what a mineral streak is is the color of the mineral in its powdered form and the way we test it is we take the sample and we rub it against an unglazed ceramic street plate these look like little tiles they come in black and white and you take your mineral and you actually rub it a little bit on the streak plate and what that does is it breaks off a little bit of the mineral in its powdered form so that you can identify the color as a powder now you might think well the color is going to be the same whether it's in a powder or not but that's not necessarily the case if we look at some examples so this is Galena and Galena does look kind of a metallic silver color when it's whole and then when you do its streak it looks similar but it's almost more of a blackish color sulfur gives you a yellowish white streak azurite gives you a blueish streak and then something more complex like calc and theit gives you almost a white streak even though the mineral itself appears blue so that streak the color of the mineral as a powder but we want to look at additional properties or characteristics as well so let's look at luster so what mineral luster is is the way in which light reflects off of the surface of the mineral there are two main types metallic and nonmetallic and then there are some additional types of luster that you may come across things like vitreous pearly silky waxy etc but again the two main types are metallic which would be minerals that you can describe as actually looking like chunks of metal so these are going to tend to be gold brassy silver kind of colors very reflective with kind of the like sparkling off of the surface this is as opposed to a nonmetallic mineral like this potassium feldspar and olivine here which look more dull and less like metals so that's luster then we have breakage breakage is a term I use to refer to how the mineral breaks apart alright the way in which the mineral sample will tend to break and again we have two main types of breakage the first is cleavage mineral set display cleavage they will break along smooth planes parallel to where the weakest bonds are the way you can identify this is by looking for samples that almost look like they have been cut by human beings but in fact that's breakage in the form of cleavage they're breaking in a predictable in a predictable way as opposed to cleavage we have fracture minerals set display fracture they're gonna break along more irregular or curved surfaces without much of a definite shape and the best way to visualize this is to see some examples so here are three minerals this is biotite mica on the Left which displays cleavage it breaks into thin flexible sheets in the center we have calcite and on the right we have Galena all of them look as if they've been essentially cut with some sort of blade but that's just how they break apart the opposite would be fracture these samples all display fracture like this olivine on the right here and they look like they're broken kind of randomly there's no predictable shape if you were to hit them with a hammer they would just break into kind of a random shape so that's breakage then we have hardness and this is exactly what you might think it's how hard a mineral is or in other words how much the mineral will resist being scratched and to figure out hardness we have a scale that we use it's called the Mohs scale of hardness and it's a scale that goes from 1 to 10 with 1 being soft and 10 being hard and here you can see different minerals and where they fall on the Mohs scale of hardness so one of the softest minerals known to man is talc that has a 1 on the hardness scale and you can actually break it apart with your fingernail it's very soft going all the way up through gypsum calcite fluorite getting harder apatite orthoclase harder stale quartz topaz corundum and then eventually diamond which has a hardness of 10 it's the hardest mineral that is known to man now the way we test this is by trying to either rub mineral samples against one another to see which is harder and which is softer or to rub them against some known surface or some known substance something like the copper you find in a penny which has a hardness of 3 or a piece of glass which is commonly used which has a hardness of 5.5 so a typical test would be to take a mineral and try and scratch a piece of glass and if it does scratch it you know that mineral has a hardness greater than 5.5 if it does not leave a scratch on the glass and it would be less than five point five so that's hardness and then finally we have this other category and there are a bunch of other characteristics that we can look at and I'll give you a few examples certain minerals react when exposed to acid so like calcite for example will fizz up and bubble when you put weak acids on it dolomite does the same thing but only when it's powdered some rocks will glow under ultraviolet light like fluorite it gives a very impressive fluorescent glow when you shine a ultraviolet light on it the mineral calcite displays double refraction which means when you look through it it will reflect refract the light so that you're seeing double of whatever is on the other side additionally we got samples like magnetite which is magnetic so it's a good way to test it and then things like taste and smell he light will actually taste salty it's also known as rock salt or sulfur which will actually smell kind of like rotten eggs one important thing to keep in mind is that all of the minerals physical characteristics result from the internal arrangement of atoms and that means the way in which the atoms are set up inside the mineral is what gives them all of these characteristics from color luster streak hardness etc all of those result from the way that those atoms are arranged and ordered and bonded together within the mineral thanks for watching don't forget to subscribe and like on YouTube thanks