Included crystal-A mineral crystal that is trapped within a gem while it is growing. This crystal can be the same crystal as the gem it is trapped inside. It can also be many shapes such as angular or rounded. It can also be different colors, light, dark, transparent or opaque.
Negative Crystal- This is a space that might have liquid, gas or both inside a gemstone. It resembles a mineral inclusion but does not have the mineral. You see these in the beryl gemstone like an emerald.