The Great Diamond Authority

"Every Gem is made with a purpose: to serve the order of the Diamonds. Those who cannot fit inside this order must be purged!"

The Great Diamond Authority is the matriarchal body of Gem leaders who rule in absolute power over the Gem Homeworld and all still-existing Gem colonies.

Symbol
The symbol of the Great Diamond Authority appears on many Gem structures and has changed over time. On structures mostly built before the Rebellion, the symbol consists of four diamond shapes: White (top), Yellow (left), Blue (right), and Pink (bottom). On modern structures, as well as on the partially-healed Centipeetle Mother's drawings that are seen in "Monster Reunion", the Pink Diamond symbol has been removed, leaving only the White, Yellow and Blue symbol shapes (now depicted in the form of overlapping triangles). In addition to appearing on structures, the new symbol appears on the floor of every modern Gem ship.

Yellow Diamond
Yellow Diamond is one of the Diamond matriarchs. She is the former superior of Peridot, and also the current superior to countless other Gems made for her. She commenced the Cluster project to acquire it as a geo-weapon after the Earth was deemed unfit to be a colony due to the rise of the Crystal Gems.

According to Peridot in "Hit the Diamond", Yellow Diamond is in complete control of Homeworld's military.

Almost all of her subordinates (except her Pearl, "Doc" and "Navy") have a small yellow diamond insignia on their chests in two symmetrically connecting diagonal black lines.

Subordinates

 * Yellow Pearl
 * Topaz
 * Peridot (formerly)
 * Jasper (originally Pink Diamond's subordinate)
 * Prosecuting Zircon
 * Rubies
 * Ruby (Doc)
 * Ruby (Eyeball)
 * Ruby (Army)
 * Ruby (Navy)
 * Ruby (Leggy)

Blue Diamond
One of the Diamond matriarchs. She was the superior of Ruby and Sapphire, and many other Gems made for her. She was the supervisor of the colonization of Earth. Her subordinates used to have a large blue diamond on their bodies, but now they have a similar design to Yellow Diamond's subordinates, with a small light Blue Diamond insignia on their chests in two symmetrically connecting diagonal dark lines.

Lapis Lazuli has a blue diamond like symbol on her dress, implying she may have had some sort of connection to Blue Diamond's court.

According to Rebecca Sugar, blue-colored Gems are oriented towards diplomatic roles.

Subordinates

 * Blue Pearl
 * Holly Blue Agate
 * Aquamarine
 * Sapphire (former court member)
 * Several Rubies
 * Ruby (formerly)
 * Unknown court members
 * Several former subordinates of Pink Diamond
 * Amethysts
 * Jaspers
 * Carnelian
 * Defending Zircon (alignment unknown)

Unknown White Diamond
One of the Diamond leaders. Details about her are unknown except her white symbol that appears alongside those representing Blue Diamond and Yellow Diamond on both ancient and modern Gem structures. Her name is never stated, but due to consistencies and naming patterns, it is most likely White Diamond.

She appears to have spiky hair, and her gemstone is placed on her forehead according to her mural. Also, according to her mural, she had the most Gem Colonies when the Moon Base was built. However, it is unknown how many she has now.

Pink Diamond
A former Diamond matriarch. Details about her are unknown other than that she was in charge of the Earth colonization and occupation efforts, and that her symbol is present on the majority of ancient Gem structures, but absent on structures dating as early as the Pyramid Temple, as she was allegedly shattered by Rose Quartz, one of her former subordinates, at some point during the Rebellion. She also has a mural in the moon base, along with all the other Diamonds.

Pearl's space suit, as seen in "Space Race" and "Back to the Barn", has the Pink Diamond insignia on its chest. This implies that Pearl was somehow previously involved with Pink Diamond before her destruction. Sardonyx also sports pink diamonds on her feet, and this most likely comes from Pearl.

According to Eyeball in "Back to the Moon", Pink Diamond was shattered by Rose Quartz. In the following episode "Bubbled", Garnet confirms that Rose did shatter Pink Diamond. This likely occurred between 6,250 and 5,750 years ago, taking into account that Jasper (who, as explained by Peridot, was created halfway or so through the war) had been originally assigned to her, that Blue Diamond was in charge of the Earth colonization efforts 5,750 years ago (when Garnet first formed), that Centipeetle drew only 3 diamonds when recounting the end of the Rebellion (which happened more recently than 5,300 years ago, when Bismuth was bubbled), and that the Rebellion took place over roughly 1,000 years. Pink Diamond also owned a human zoo, which she used to store humans to showcase as trophies of her conquests. However, in "The Trial", it has been suggested by the defending Zircon that Rose Quartz couldn't have been the one to shatter Pink Diamond, but perhaps a Diamond. Her evidence is that Rose Quartz was a recognized threat for hundreds of years, so no Rose Quartz soldiers were in Pink Diamond's entourage. None of Pink Diamond's soldiers, Sapphires or her Pearl saw Rose Quartz anywhere near her.

Past Subordinates

 * Rose Quartzes
 * Rose Quartz
 * Bubbled Rose Quartzes
 * Amethysts
 * Jaspers
 * Jasper
 * Carnelian
 * Pink Diamond's Pearl
 * Sapphires
 * Agates

Influence
The Great Diamond Authority has great influence on Gems of lower castes and members of their courts. Most Gems wear a colored diamond emblem on their outfit that corresponds to the Diamond they serve. Members of a Diamond's court are known to show respect, such as Sapphire calling Blue Diamond "[her] Diamond". Some members are passionate and enthusiastic about working for a Diamond. For example, Peridot once exclaimed, "I'll never forsake the Gem I was made for!", and Holly Blue Agate openly spoke of Blue and Yellow Diamond's greatness.

The loyalty Gems have for their Diamonds is such that some will do anything to avenge their Diamond. In addition to being widely regarded as a tragedy, Pink Diamond's death had incited some Gems, notably Jasper and Eyeball, to seek vengeance on her behalf. Many Era 2 Gems appear to be largely unaware of the Rebellion, evidenced by Peridot's ignorance of the Crystal Gems in "Marble Madness". This suggests that events about Pink Diamond's death are not frequently discussed, which may be indicative of the devotion and respect Gems have for the Diamonds.

Trivia

 * The confirmed instrument of the diamonds is a synthetic sound combining harmonette and strings, processed by a synth, this can also be heard in "Same Old World" and "Monster Reunion" when the Corrupting Light flashes.
 * The current symbol might be a reference to the Triforce symbol from The Legend of Zelda, as they both are three connecting triangles that form a symbol. It also bears a resemblance to the Mitsu uroko emblem of the Hōjō clan.
 * The former symbol resembles the NFPA 704 diamond symbol, with slightly different colors (one of the diamonds is red instead of pink) and with the colors' positions switched.
 * The former symbol's order of colors seems to represent the location of the gem in the body of its owner: both Blue and Yellow Diamond have their gem in their chests, so they are equal in position in the middle row, whereas White Diamond has her gem in her forehead and Pink Diamond has it in the lowest position in her navel, hence in the symbol White Diamond is on the top and Pink Diamond is on the bottom.
 * The Great Diamond Authority is yet another of Ronaldo Fryman's paranormal theories that has been proven to be true.
 * He claimed his theory in the first season episode "Keep Beach City Weird", and Peridot confirmed the matriarchs' collective name in the episode "It Could've Been Great".
 * It is revealed in "Monster Reunion" that the Diamonds were the ones responsible for the Corruption of almost all remaining Gems on Earth.
 * Centipeetle only drew three diamond symbols when she was asked who or what caused the damage to her and the other Corrupted Gems, so one of the Diamonds was not involved with this weapon, presumably Pink Diamond, who was shattered during the Rebellion, while the damage was caused at the end of it. Centipeetle's drawing depicted the original symbol of adjacent diamonds (with Pink Diamond's removed) rather than the modern symbol of overlapping triangles.
 * The circles placed behind the heads of the Diamonds in their murals resemble halos, a common motif in the sacred art of Ancient Greece, Ancient Rome, Hinduism, Buddhism, Islam, and Christianity. Combined with the epithets the prosecuting Zircon uses for Yellow Diamond, it appears light is extremely relevant in their iconography.


 * So far, White Diamond is the only Diamond that has not been mentioned by the characters in the entire series, being only depicted in an indirect way.
 * Rebecca Sugar has confirmed her existence in the "Wanted" episodes as the white monument that appears in the Homeworld city, stating that she has plans for her.


 * Although gems usually serve under a specific diamond, Blue and Yellow Diamond seem to have the same amount of authority over each other's subordinates. For example, Yellow Diamond tells Holly Blue to, "Get to the point!" in That Will Be All, and she also poofs Blue Diamond's defending Zircon in The Trial.

Gallery
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