By 
As reported earlier in the week, Street Fighter X Tekken has two types of gems: Boost and Assist. There are 52 Boost gems and 5 Assist gems, for a total of 75 gems in the game. You’ll have the ability to equip three gems at a time, and each one has its own advantages and disadvantages.
Capcom say you’ll be able to select any combination of the Assist gems, which give you bonuses that are always activated while they’re equipped. Meanwhile, Boost gems provided a stat increase in one of five areas: attack, defense, speed, cross gauge acquisition, and vitality. However, Boost gems require a specific condition to be met in order to be activated.
For example, a particular speed Boost gem (it isn’t specified which) will be automatically activated after a player blocks 2 to 3 stringed attacks from their opponent. Boost gems also have drawbacks to compensate for the stat increase. Here’s one example:
Immense Power Lvl 1
Effect: +10% damage
Duration: 20 seconds
Activation: Land 5 normal moves
Immense Power Lvl 2
Effect: +20% damage
Duration: 15 seconds
Drawback: -10% speed
Activation: Land 10 normal moves
The higher level Immense Power gem gives you increased damage, but at the cost of speed, for less time, and is harder to activate. Activation conditions for gems are hidden from opponents, and yes, there are indeed multiple variants of each gem as this suggests.
You can view a complete list of the standard gems in the game at Capcom’s community site. They also sent out a large batch of screenshots, which you can check out below:
