The Gems are agents with The Authority.
First, concerning The Authority, we are told it is a "secret group formed after the carnage of World War I by a group of well-to-do families in Europe and North America". The founders "blamed the destructive world war on politics, nationalism, and greed on both sides. So they decided to form an organization that defended humanity. A secret organization immune to political, religious, and national agendas. These well-to-do families independently supported the organization as it grew in size and sophistication". Now, The Authority "answers to no government. No national or religious leaders. We pursue those who hurt the innocent for the sake of their own greed or twisted agenda".
Second, with regard to The Gems, we learn that they "are a special group of young ladies" under the command of a key leader with The Authority, Mrs. Bracket (aka Mrs. B.). These young women are still in high school though in their junior or senior years. The Gems Project was created to have a team of operatives who could "operate under the radar in areas where adults draw too much attention".
The initial members of the Gems are:
Olivia Spencer, code-named Emerald, is seventeen years old from London, England. Half English and half Jamaican. Specializes in leadership, marksmanship, and is a rated pilot. Speaks English, Spanish, and Swahili. Tends to be "overbearing with paranoid tendencies".
Miyuki Kaiko, code-named Ruby, is sixteen and from Okinawa, Japan. She specializes in gymnastics and martial arts. Trained in jungle survival and deep sea diving. Once blew up her boyfriend's motorcycle using a rocket launcher. Speaks English, Japanese, and Mandarin Chinese. Said to be impulsive, undisciplined, and a thrill-seeker.
Nadia Sarif, code-named Sapphire, is sixteen and from Riyadh, Saudi Arabia. She's a science and computer nerd. Nadia's zero-gravity school agriculture project created interest from NASA. Speaks English, Arabic and Russian. Known to be passive and socially awkward and lacking in leadership skills.
Emma Rothchild, code-named Black Opal, is a transplant from New York City who specializes in high school theater and shopping. Speaks English and French. Has trouble tolerating other people's viewpoints.