Ardana

Ardana is a Federation member world. It is the only known planet that mines Zenite. The planet's capital city of Stratos is an anti-gravity elevated metropolis known for its art and culture. The humanoid inhabitants of Ardana were divided into two castes, a labor class of Troglytes and an intellectual ruling class of Stratos city-dwellers. The caste system was riven with conflict.

Despite its membership in the Federation Ardana employs torture and capital punishment.

In 2269 the USS Enterprise came to obtain zenite for use to prevent a bacterial botanical plague on Merak II. (TOS: "The Cloud Minders")

It is speculated that this planet's Zenite has been an enormous source of wealth for it enabling the aristocratic population such luxuries as a floating city.

It's also assumed in fanon that Kirk and Spock made a full report of Ardana's social policies and the Federation was moved to pressure the planet to abolish the oppression.