I am not sure how deep Martha mine is because every day at around 12:00 the miners use dynamite to expose more rock at the bottem of the pit so its depth changes every day.
You have to mine pretty deep for diamonds (if that's what you're asking)
The Homestake Mine in South Dakota reached depths of over 8,000 feet (2,438 meters) during its operation. It was the largest and deepest gold mine in North America before closing in 2002.
In 1878 John McCombie and Butt Lee discovered gold at Martha hill and began the Mine. Waihi was then built around the mine to house the workers etc...
Deep Mine
in afraka
Martha Emmons has written: 'Deep like the rivers' -- subject(s): African Americans, Folklore
80 to 100 foot deep
a thing
The deepest mine is the Western Deep mine in Witwatersrand, South Africa; 3.3 km (presently)
The type of mine is called a strip mine.
2 kilometres
7,000,000 feet deep2133.6 kilometre deep