Definition of blue ground in English:

blue ground

Pronunciation /blo͞o ɡround/ /blu ɡraʊnd/

noun

another term for kimberlite
‘To the northwest in section 8, a group of grassy springs with some 'blue ground' were found.’
  • ‘In the early days, blue ground was dumped in big piles and the miners waited to extract the diamonds until weathering had turned the kimberlite into yellow ground.’
  • ‘When they reached the bottom of the soft yellow ground and struck the "blue ground" that lay underneath, many miners thought their claims had petered out.’