Caste System

The Galaxy Authority maintains a strict caste system with every type of gemstone having a predetermined role and place in the social pyramid, each with own their privileges and ordained purposes. Any gem who in any way digress from their roles, be it intentional or not would be considered defective. Since the penalties for such actions are so severe, most disgruntled gems either keep their dissensions to themselves or are forced to go into hiding. Because there are so many of one type of Gem, all Galaxy Gems, except the Diamonds, distinguish themselves via coded serial numbers.

Diamonds
Diamonds are the highest-ranked caste similar to royalty and referred to as the "matriarchs" of Gem society; they make up the Great Galaxy Authority. All diamonds are of a massive size, towering over other types of Gems seen and even some fusions. They all have diamond-shaped pupils in their eyes.

Almost all Galaxy Gems are fanatically loyal to the Diamonds, seeing as how Jasper 3NR formerly adored Red Diamond. Gems also appear to be categorized under their respective Diamonds as Red Diamond referred to a Raspberry Garnet as being "of her court" and a Purple Peridot saying she was "made" for Purple Diamond. Any form of infidelity displayed towards the Diamonds is considered punishable by death at the worst. Their honorific (from their subordinates) is "My Diamond."

There appears to be a caste ranking within the Diamonds themselves as Red Diamond was shown to be hierarchically superior to the other Diamonds and the leader of the Authority. Conversely, Black Diamond was below Purple and Brown Diamond and had to obey their orders.

Aristocrats
Aristocrats are high-classed gems comprising of Sapphires, Moonstones, Sunstones, and others. These gems have a lot of use for the Great Galaxy Authority. They can predict possible futures and help in other ways like hypothesis about possible endeavors.

Commander/Fleet Commander/Manager
These gems help with colonization. Commanders command gems to kill any Organic Life. Fleet Commanders can scout out planets and deploy Soldiers to wipe out life. Managers can send certain gems to do missions and manage the Kindergarteners job, making sure they do it right.

Terraformers
Terraformers are high ranking gems. They carve out planets so injectors can fit in and implant gems into the Planets Soil. The evidence of their high ranking is in the Episode "Same Old World" where Lapis is on a mission to Earth before getting caught up in the Rebellion.

Technicians
These Gems include Peridots, Hematites, and Coppers. They are certified Kindergarteners and help injectors move around Kindergartens and go on Missions evident by why canon Peridot was on mission to Earth, with Jasper as an escort.

Detectives/Law Gems
Detectives are given a case to find out what happened and why, sorta like private police. Law Gems act as lawyers for the courts of the Galaxy Homeworld. They presumably have no choice over what cases they prosecute or defend for (as revealed in "The Trial") and are assigned cases instead.

Construction
Construction Gems build tons of Homeworld structures. They include Bismuth, Sandstone, Granite, and Irons. They mostly help with Brown's schematics for new buildings on the Homeworld or it's outlying colonies.

Soldiers
There are two types of Soldiers

Quartz Soldiers - Made of Quartzes. They are less valuable than other gems. They guard facilities for the Diamonds

Foot Soldiers - They guard higher up gems since they're invaluable and can be replaced easily. Smarts is not a need for these gems.

Servants
These Gems are made to serve higher up gems. They are supposed to follow behind their masters and are supposed to hold/carry their masters things and open doors for them. Each Diamond has their own Personal Pearl, but, Red Diamond has two pearls.

Pebbles
Not much is known about a Pebbles Purpose but they are servants in Green and Pinks Palace