If handed a hard material, it can't immediately be assumed that it is a rock even if it might look or feel like one. To tell what this certain hard material is, its appearance can get you started. Minerals, while solid and compact like rocks, are naturally occuring crystalline solids. This means that they are made of crystals that are arranged in an orderly, 3D pattern. If the hard object looks to be constructed like this, then it could be a first clue towards it being a mineral. To be sure, though, further tests need to be done. Look to see if the object leaves a streak (the color that is left behind when the material is rubbed on a porcelain tile), check its luster (the light that is transmitted by the mineral, aka whether it's shiny or not), its hardness (the ease with which a mineral is scratched) and its cleavage (how smoothly it breaks apart) and magnetism. These are the usual tests that are "performed" on an object to find out what kind of mineral it is. If this object is a rock, though, you can usually tell this based on its grain size (the size of the "pieces" it is made out of). This can lead to many things about the type of rock and its origin. If it has large grains it is intrusive, meaning it cooled inside of the Earth for many years. If it has small grains it is extrusive, which has cooled on the exterior of the Earth for a shorter period of time. Appearance also can classify the object into one of the three rock groups: igneous, sedimentary, and metamorphic. For example, if the object has many rocks that appear to be cemented together it is a sedimentary conglomorate rock. If it has bands, then it is a folliated metamorphic rock. These are only a few of the many ways rocks can be "narrowed down" and classified.
To people who haven't studied the difference between rocks and minerals, certain types may look similar to each other. Something that looks like a rock could instead be a mineral. Also, all of the tests that are used to find out whether or not something is a mineral could work on rocks. This is because rocks are made up of minerals. However, you can be sure that, for example, an object is a mineral and not a rock because these tests should have the object match up with a certain mineral. This is especially seen through the Mohs Hardness Scale which, based on an objects hardness, will accurately match up what type of mineral something is.
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