This is what White Diamond expects of all of us...! From a thin flake of mica to the deepest, hardest stone, we all must make sacrifices for the sake of our perfect empire!
|—Yellow Diamond, "Change Your Mind"|
Prior to Era 3 the Gem Homeworld maintained a strict Caste System with all types of gemstones having predetermined roles and places in the social pyramid, each with their own privileges and ordained purposes. Gems who in any way deviated from this, be it intentional or not, were considered defective. Since penalties for such actions were severe most disgruntled Homeworld Gems either kept dissensions to themselves or went into hiding. Because there were so many of each Gem-type (except Diamonds) all Gems distinguished themselves via serial numbers. The Caste System was divided up under the rule of each Diamond. If Gems were to greet or refer to another in a higher section of the Caste System they normally prefaced their Gem name with "My" to show they were their superior(s) (i.e. "My Diamond", "My Hessonite", etc).
- Main article: The Great Diamond Authority
Diamonds were the highest-ranked caste similar to royalty and referred to as the matriarchs of Gem society; they still made up the Great Diamond Authority. All Diamonds were (mostly) massive in size towering over other Gems and most Fusions seen. They all had diamond-shaped pupils in their eyes.
Almost all Homeworld Gems were fanatically loyal to the Diamonds; they also appeared to be categorized under their respective Diamonds as Blue Diamond once referred to Sapphire as being "of [her] court" and Peridot 5XG said she was "made for" Yellow Diamond. Infidelity displayed towards the Diamonds was considered punishable by death at the worst. Their honorific was "My Diamond".
There appeared to be rankings within the Diamonds themselves as White Diamond was hierarchically superior to the other Diamonds and the leader of the Authority. Conversely, Pink Diamond was below the other Diamonds and had to obey their orders.
Emeralds were high-ranking gems. In The Steven Universe Podcast Rebecca Sugar and Ian Jones-Quartey emphasized that Emeralds (specifically the one in "Lars of the Stars") are elite Gems in charge of fleets. The only known Emerald had at least three ships (her personal shuttle, the Sun Incinerator and Destiny Destroyer) and was in charge of an unspecified amount of Gems.
- Emerald - An Emerald whose primary craft was stolen by Lars Barriga and the Off Colors who she continued following ever since in her imperial warship to reclaim her most prized possession from them.
Morganites were also high-ranking Gems. While their exact roles remained unknown they were high enough to have their own Pearls and Rubies.
- Morganite - A Morganite mentioned by Rhodonite as having replaced her components after discovering they had fused.
- Main article: Aquamarines
Aquamarines were another type of Gem with a higher rank. They appeared to serve as assistants to Diamonds using their own ships to travel from planet to planet and collect things they wanted. Rebecca Sugar said Aquamarines were high-ranked blue Gems.
- Main article: Sapphires
Sapphires were of the nobility class described as rare Gem aristocrats and part of the elites; in spite of this they had no immunity from outcast status. They could see imminent events using their future vision; Sapphires were the only normal Gems with this ability. Their honorific was "Your Clarity". Known subtypes included Padparadschas.
Padparadschas were a subtype of Sapphires. However, the only one seen could have visions of events in the past just a few moments after they happened.
While the exact roles of Garnets were unknown they seemed to be higher-ranking as the only true caste member seen is in charge of lower-ranking Gems. Subtypes include Hessonites, Demantoids and Pyropes as mentioned by Blue Diamond in "Together Alone". The Fusion Gem Garnet apparently had no relation despite sharing a name as Blue Diamond was surprised to hear she called herself one.
While the exact roles of Hessonites were still unknown they appeared to be commanders. The only one seen was Nephrite's ex-leader. She issued her and her crew the order to travel to Earth and retreat from the incoming Diamond attack. She returned in Save the Light marking her official debut in the series canon. Like the one mentioned some Hessonites were tall with poofy hair. Their honorific, similar to that of the Diamonds was "My Hessonite".
- Hessonite - The former superior of "Squaridot" and Nephrite and former owner of the Light Prism who commanded the latter Gem and her crew from the colonization of Earth until the end of the Rebellion. She traveled back to Earth to retrieve the Prism after losing it during a fight with Rose Quartz once again encountering the Crystal Gems.
Demantoids were a subtype of Garnets mentioned by Blue Diamond.
Pyropes were another subtype of Garnets mentioned by Blue Diamond.
- Main article: Lapis Lazulis
Lapis Lazulis were extremely valuable to the Gem Empire. As stated by Yellow Diamond it was known that Lapis Lazulis were made for terraforming. Peridot 5XG also said they were typically partial to water and flying. Their use for terraforming planets likely explained one's ability to manipulate water with ease (and possibly enjoying farming).
- Main article: Jades
While their exact roles had not been shown Jades appeared to be high in the Caste System given they attended the Era-3 Ball. Unlike most Gems Jades had differences between their physical appearances depending on which type of Jade they were.
- Main article: Nephrites
Nephrites were in charge of piloting Homeworld Dropships to begin colonizations and served as pilots for various other spaceships; they also started building on colonies. Their ranking was never clearly stated but appeared to be high considering they captained their own ships and Yellow Diamond contacted one directly in "Jungle Moon" which she would not do with lower-ranking Gems. Numerous Nephrites were corrupted with one (known to Steven Universe as Centipeetle) formerly being a captain in charge of other Nephrites under Hessonite's command and leading a dropship that went to Earth.
- Main article: Topazes
Topazes seemed to be soldiers obeying orders and acting as bodyguards for assigned Gems; these were traits shared with Quartzes and Rubies. A fusion of two was sent to Earth by the Diamonds alongside Aquamarine to find human beings to put in Pink Diamond's Zoo. These Topazes were efficient at trapping and engulfing others within their fusion-form. Topazes also acted as guards of places suitable for more elite Gems as seen in "Familiar". Rebecca Sugar said Topazes were high-ranking yellow Gems.
Zircons acted as lawyers for the courts of Homeworld. They had no choice over what cases they prosecuted or defended for as revealed in "The Trial" and were assigned them instead. In the podcast Rebecca Sugar and Ian Jones-Quartey said they had a sort of medium rank serving the upper classes but having no individual power.
- Blue Zircon - A Zircon who defended Steven during his trial.
- Yellow Zircon - A Zircon who acted as the prosecutor during Steven's trial.
- Main article: Peridots
Peridots serves mainly as technicians and Kindergarteners sometimes performing field assignments on other planets such as the Peridot who befriended Steven and joined the Crystal Gems. Being workers Peridots had a low rank only being allowed into elite Homeworld areas if a job was needed to be done there.
In Era 2 Peridots were given Limb Enhancers to compensate for the lack of strength and unique abilities older Gems had due to the depletion of resources on Homeworld. Peridot 5XG was shown to have ferrokinetic abilities.
- Main article: Quartzes
Quartzes, like Topazes and Rubies were soldiers. Made to fit the roles of elite warriors Quartzes normally had incredible height, broad shoulders and an intimidating muscular build. Rose Quartz and Jasper both fit this description; Amethyst did not fit the description because she "stayed in the ground too long" and was therefore "overcooked". Some Quartzes were used as bodyguards and escorts as shown in Jasper's case. They appeared to be less numerous than Rubies though greater than Topazes. According to Ian Jones-Quartey some had defensive powers as well like Rose Quartz since "they can't all be tanks". Quartzes were described as being "huge, loyal soldiers". Jasper stated Quartzes were made to fight and her kind specifically always got what they wanted. Some also acted as elite guards at Homeworld outposts such as Pink Diamond's Zoo or like the Quartzes commanded by Emerald and Hessonite. They were Gems commonly made on Earth and the most diverse known Gem-type with subtypes including Agates, Amethysts, Carnelians, Citrines, Jaspers and Rose Quartzes.
Agates were Quartzes that seemed to have a higher ranking than standard made-for-battle ones with roles as administrators. Yellow Diamond stated in "What's the Use of Feeling (Blue)?" that they were meant to be terrifying figures intimidating Gems under them into obedience. In "The Trial" it was revealed they could also be bodyguards for Gems such as Diamonds. It could be assumed that based on the way Holly Blue Agate acted around Sapphire and the Diamonds that while having some authority Agates were not higher-ranking Gems at least when compared to Sapphires.
Citrines were a subtype of Quartzes who seem to be elite guards serving high-ranking Gems.
Rose Quartzes were new compared to other Gems having been created on Earth. Sometime between the start of one's rebellion and Pink Diamond's shattering every Rose Quartz in existence was bubbled and made to reside in Pink Diamond's Chamber in her Zoo. It was stated in "That Will Be All" that Blue Diamond wished to keep them around for the sake of preserving Pink Diamond's legacy while Yellow Diamond wanted them shattered as they believed one to be responsible for the start of the Rebellion and Pink Diamond's destruction although this was not really the case. While still being soldiers Rose Quartzes were apparently known for defensive powers rather than the offensive abilities other Quartzes had.
Amethysts were a subtype of Quartzes with purple coloring. The Prime Kindergarten on Earth produced Gems of this type. Amethysts acted as soldiers and/or guards as seen with the Amethysts guarding Pink Diamond's zoo.
Carnelians were a subtype of Quartzes with maroon-red coloring. The Beta Kindergarten on Earth produces Gems of this type. Based on other Quartzes it could be assumed they were Gems of the soldier type as well.
Jaspers were a subtype of Quartzes mostly shown to have tangerine skin and red-orange markings though some were different colors, shapes and sizes depending on the kind of Jasper they were. Similar to other Quartzes below Agates they acted as either soldiers or guards.
Tiger's Eyes were a subtype of Quartzes yet to be seen but mentioned by name.
Other Quartzes lacking specific gemstone identifications.
Bismuths were builders for aristocratic members of Gem society. As such they possessed a broad stature for intense physical labor, above-average resistance to heat and damage and hands capable of fluidly changing form without the need for typical Gem shapeshifting to fit a wide variety of purposes.
- Bismuth - One of the original Crystal Gems who was poofed and bubbled by Rose Quartz and later Steven when she developed a weapon devised to shatter Pink Diamond unaware Rose and Pink were one and the same. She permanently rejoined the team after "Made of Honor".
- Main article: Rubies
Rubies were another soldier caste and nearly the lowest-ranked of all Gems. They also filled the roles of personal escorts and bodyguards as well even acting as scouts on recovery missions. Due to their numbers individual Rubies were considered expendable footsoldiers or cannon fodder and much of their worth in Homeworld's armies comes from fusing with each other.
Rubies had almost no differences in appearance and were not supposed to have different personalities; the fact they did "flies under the radar" because they mostly acted serious around higher-ranking Gems.
Spinels were entertainers for those designated their "best friend". They were implied to be rare as Pearl stated that Steven was "a lucky one" for acquiring such a Gem. The body of the only one seen was more elastic than that of any other Gems even going beyond the movements of Bismuth. According to Rebecca Sugar their gem cuts are shaped like playing card suits (hearts, clubs, spades, and diamonds).
- Spinel - The main antagonist of the movie who was close to Pink Diamond before being given Earth; she played a game with Pink by waiting in her garden for 6,000 years until Steven brought down the Caste System and Empire. Upon realizing the true purpose of Pink Diamond's "game" she furiously traveled to her former friend's colony armed with a modified Injector and Gem Rejuvenator to destroy both the planet and her son. She eventually gave up and went back to Homeworld with the other Diamonds.
- Main article: Pearls
Pearls were a servant caste and had such a low rank they were not even considered real Gems but instead viewed as property. They were expected only to serve and be submissive and obedient simply waiting on their owners until being told "That will be all" and not acting independently in any way. Pearls also provided simple luxuries like singing, dancing and visual entertainment by projecting holograms.
Unlike other Gems Pearls did not have a set uniform as they could be customized in colors and appearances. The position of a Pearl's gemstone was made to match that of their owners.
- Main article: Pebbles
Pebbles also acted as servants but unlike Pearls who belonged to individual Gems they appeared to serve everyone. They had building and sewing skills that were enough to fulfill different tasks at incredible speed.
- Main article: Fusion Gems
Fusions (specifically Same-Gem Fusions) were used as weapons, especially in times of war and solely for combat being seen as objects rather than their own beings. Fusions outside of battle were considered inappropriate and unorthodox, regarded as disgusting, embarrassing or discomforting to behold as inferred from Jasper and Peridot 5XG's reactions towards Garnet. However, the existence of Topaz revealed that despite this Fusions outside of battle were indeed legal on Homeworld provided they were of the Same-Gem type and could only be allowed for certain castes (e.g. soldiers).
To a further extent only Fusions of the same type were seen as acceptable such as Fusions consisting of Rubies or Topazes. Fusions between Gems of different varieties were considered an abnormality as the Gems of Blue Diamond's court referred to Garnet as "disgusting" and "unheard of". As other examples Rhodonite and Fluorite were forced to hide to avoid being shattered; Rhodonite's components were even replaced by their Morganite after she found out they liked to fuse. The reasoning for prejudice against Different-Gem Fusions was because they created an entirely new Gem which disrupted Homeworld's society; the new Gem could have had no place in the Caste System and thus hold no job beneficial to Homeworld.
Gems lacking known Gem-types and/or societal roles.
- Desert Glass - A formerly-corrupted Gem seen in "Steven's Lion" with the ability to create structures out of sand.
- Watermelon Tourmalines - Not much is known about these Gems.
- Snowflake Obsidian - A formerly-corrupted Crystal Gem mentioned in "Bismuth" . She was uncorrupted in "Change Your Mind" and resided in Little Homeworld.
- Rutiles - Not much is known about Rutiles though they seem to have piloting capabilities.
- Larimar - A formerly-corrupted Crystal Gem mentioned by Bismuth nicknamed "Little Larimar".
- Beryl - A formerly-corrupted Crystal Gem mentioned by Bismuth.
- Serpentine - A formerly-corrupted Crystal Gem mentioned by Bismuth.
- Pyrites - In "Familiar" Blue Diamond mentions she lets Pink Diamond name a batch of Pyrites as Fool's Gold.
- Comby - A Gem in the shape of a hairbrush who serves Blue Diamond.
- Kyanites - In "Change Your Mind" Blue Diamond mentions she lets Pink Diamond bring alien worms to Homeworld from a colony of Kyanites.
Defective Gems, also referred to as being Off-Color served no use to the Empire, were cast out of its society and if caught were shattered. The only exceptions were the Quartzes stationed at Pink Diamond's Zoo kept in service by Blue Diamond. Amethyst was another exception provided she wore Limb Enhancers like Era-2 Peridots to reach her "height requirement".
- Main article: Corrupted Gems
Corrupted Gems, also known as Gem Monsters were Gems who became corrupted by the Diamonds after the Rebellion assuming monstrous and nigh-incoherent forms. One of the main objectives of the Crystal Gems other than the protection of humanity and Earth was to defeat, contain and hopefully cure these Gems. They did not exist on Homeworld and as such had no place in its society.
Cluster Gems, otherwise known as Gem Mutants were originally Crystal Gems shattered into Gem Shards during the Rebellion and fused against their will into monsters similar to Corrupted Gems. The Cluster was a result of the Diamonds attempting to harness this process to create a "geo-weapon" which would first destroy Earth and eventually other planets as well.
- This utilitarianism or functionalism-inspired system of judging an individual's worth based only on their generalizations was similar to the Caste System and Functionism from Transformers, specifically the Aligned series and 2005 IDW Generation One reboot.