No, diamond is relatively rare.
There is no pronoun that means 'abundant source'. Some nouns that mean 'abundant source' are mine or well. Some adjectives that mean 'abundant source' are much and rife.
Now Romania hasn't an abundant source of energy.
The most abundant source would be in glacial form as frozen water, although the most abundant and accessible source is groundwater.
One source of diamond is volcanic pipes.
Romania has energy resources but not so abundant.
Coal is the most abundant in the USA
Solar.
Solar.
The sun
Bolivia and Chile
yes
The people in Russia do have an abundant energy source. Russia is a world leader in the production of renewable energy, mainly through hydroelectric power sources.