FREETOWN, SIERRA LEONE - Evangelical preacher Emmanuel Momoh prayed for five years that he would discover the diamond he needed to pull his family out of poverty in eastern Sierra Leone.

The 39-year-old pastor obtained his first mining licence in 2012 when the paltry income he received from the Deeper Life Church in Kono, the country's key mining district, was stretched too thin for his growing family.

On March 13, the pastor was working in a village named Koryadu when a cry went up from one of his men in Krio, the most widely spoken language in Sierra Leone.

"God don bless we tiday," the worker shouted, brandishing a rock the color of pale honey and as large as a child's fist.

At 706 carats, an amount that would later rise to 709 when it was placed on the government's official scales, Momoh's diamond was between the 10th and 15th largest ever found worldwide, experts told AFP.

He made a decision about the diamond.

"Being a man of God, I decided to hand it over to local authorities," Momoh said, a choice that caused a global sensation, and he was soon invited to Freetown to meet President Ernest Bai Koroma.

As a self-employed miner with a valid government permit, Momoh is entitled to the proceeds of the sale due on April 5 in Freetown, apart from the four percent the government legally takes for valuation and export, plus an undetermined level of income tax.

Momoh has emphasised that his workers will also benefit from what could be an astronomical sum of money.

Without a professional assessment of the diamond's potential flaws and coloring, it is impossible to value the stone.

However, a polished stone cut from the Jonker, which is the 10th largest gem-diamond ever recovered at 726 carats, will go on sale in Hong Kong in May.

A single 25-carat portion of that stone is likely to sell for $2.2 million to $3.6 million, or $88,000 to $144,000 for a single carat, according to one expert consulted by AFP.

Momoh is clear where the money will go: straight back to Kono, where he was born, to develop his mining business, support his wife and three children, and to the local community where so many live in desperate circumstances.

"The people dealing with the diamond," he said, "I hope they are as honest with me as I have been with them."