Dangote's net worth has dropped from nearly $20 billion to just $19 billion in the past 24 hours.
However, he remains one of the few billionaires who has seen impressive gains since the year began.
Dangote's net worth is still up by $832 million this year.
Dangote owns an 86-percent stake in Dangote Cement Plc, Africa's largest cement producer.
The $100-million increase in his net worth in June follows a $300-million decline in May.
Dangote owns an 86-percent stake in Dangote Cement, Africa's largest cement producer.
But with his fortune of $20.3 billion, he remains Africa's richest man.
Dangote derives nearly half of his $20-billion fortune from his 86-percent stake in Dangote Cement.
Dangote is the founder of Dangote Industries Limited, a Nigerian conglomerate with diverse interests.
The refinery project is still on track to be completed by 2023.