Gems (Crash Bandicoot)

A Gem is an item found in the Crash Bandicoot series

Overview
These powerful jewels are hidden on Earth. About 42 of them are known to exist, though no one really knows their exact number. They seem to be a little less powerful than the Power Crystals, since a significantly bigger number is required for the same effect of 25 Power Crystals. Crash Bandicoot collects the Gems many times, for different reasons. He used them as a passageway to rescue Tawna, as a power source for Dr. Nitrus Brio's laser, and so that Doctor Neo Cortex couldn't get them instead. The Gems are always used for good, whereas the Crystals are attempted to be used for evil. Possibly stating that the Gems are filled with good, positive energy whereas the Crystals are filled with evil, negative energy. Most of the Gems are clear and transparent, but there is also a set of Colored Gems, often found in the colors Red, Yellow, Green, Blue, and Purple. These serve as platforms or lifts to secret areas.

The Gems Throughout the Games
Gems are much harder to get than Power Crystals. They're not just hidden somewhere. In almost all of the platform games, the Gems are usually achieved by breaking all of the Crates in a level.

In Crash Bandicoot, the Gems are achieved by both breaking all of the crates in a level and getting through it without losing a single life.

From Crash Bandicoot 2 onwards, the Colored Gems are hidden, and getting through a level without losing a life is no longer required to achieve a Gem. However, it has been replaced by "death platforms" (platforms with a skull) that are only accessible by not losing a life. They are generally extremely hard. They also unlock "gem platforms" that also have a clear gem a the end.

In Crash Team Racing and Crash Nitro Kart, there is no Clear Gems, only the five Colored Gems, which are achieved by winning their respective Cups, which are unlocked by collecting all their respective Tokens. The Yellow Gem is absent from Crash Nitro Kart.

In the Nintendo DS version of Crash of the Titans, Gems are awarded for completing any of the following in a level: Smash all the Crates, get all the hidden Tiki Masks, collect a certain amount of Mojo or complete the levels special event. The gem colour depends on the task that was completed.

In Crash Bash, all the Gems are green in color, and are achieved by winning a mini-game in the alotted time, usually with the odds against you.

In Crash Bandicoot Purple: Ripto's Rampage, the Gems are achieved by winning Bonus Rounds and breaking all of the Crates in a mini-game.

In Crash Twinsanity, the Colored Gems (plus a Clear Gem) appear in each level. They're hidden in secret spots.

Achieving all of the Gems in a game usually results in the player achieving the "good ending" of the game, with the exception of Crash Twinsanity, where achieving all the Gems wins the player a special FMV.

Trivia

 * Much like the Power Crystals appeared in every Crash game except Crash Bandicoot, the Gems have appeared in every Crash game except Crash Tag Team Racing, in which they gave it the name Power Gems.