Janus VI was the location of a major Federation mining outpost, it was first colonized by Humans in the 2210s. In 2267 contact was made with the native Horta, expert miners by nature, after a rocky first contact the two groups learnt about each other and formed a mining alliance, making Janus one of the most productive and profitable operations in the know galaxy, sourcing raw ore and rare elements to the entire Federation. (TOS episode: "The Devil in the Dark"; DS9 novel: Devil in the Sky)
In 2267, Commander Krell reassured his men they would look back on the sedate world of Neural with pride from palaces once they had conquered it and mined its rich mineral wealth to the core. (TOS comic: "The Order of Things")
Cardassians only typically mined on class M worlds, as it is not as cost effective to maintain operations in other non-native environments. Cardassian mining operations included the Xoxa colony and perhaps most famously Bajor, which they intensively mined during their occupation of the planet. The Cardassian operations left Bajor stripped of its resources and its own mining industry devastated. In 2370, in an attempt to revitalise Bajoran mining, a group of Bajoran private investors, in conjunction with the Federation, arranged for a family of Horta to be transported to the planet, in the hope their expert mining instincts would find deposits of minerals and ore the Cardassians missed or deemed too difficult to extract.
En route to Bajor the ship carrying the Horta was attacked by a Cardassian vessel which kidnapped the adult Horta. The Horta’s eggs arrived safely at Deep Space 9 but she was unaware of this and the Cardassians claimed they would damage her eggs unless she worked for them in a mine on the moon of Davonia. A rescue team soon retrieved the Horta and a group of fifty Bajoran slave labourers the Cardassians had working in their mines. However the Bajoran government, unaware of the private arrangement, refused to allow the Horta to settle of Bajor under ecological grounds. Instead the family settled on the Bajoran moon The Prodigal where they discovered valuable deposits of uranium, pergium and latinum. (DS9 novel: Devil in the Sky)