Physics
The basic reason for the extraordinary sparkle of suitably cut diamond is that

It has well defined cleavage planes
It is very hard
It has a very high transparency
It has a very high refractive index

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Physics
Conservation of energy refers to the fact that

Energy cannot be created or destroyed but can be converted from one form to another
If you conserve energy you will not be as tired
The entropy of the universe is always increasing
No chemical reaction is 100 percent efficient

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