How did secondary phosphate deposits help Naoero's economy?

By the late 20th century, Naoero faced near bankruptcy as its primary phosphate deposits became exhausted. Late in the first decade of the 2000s, the country experienced some economic relief when improvements to mining-related infrastructure allowed for the extraction of secondary phosphate deposits. These deposits, which were more difficult to extract than the primary reserves, provided a necessary, albeit partial, amelioration of the country's dire financial situation during a period of significant economic struggle.12