There is no definitive way to value the 20% of Manna yet. Ultimately it comes down to many factors regarding the nature of the deposit (grade, depth, cost of extraction and distance to port). The two ways we would have a solid idea of its value is;
1) What someone is willing to pay for it
2) If Manna goes into production and we can calculate 20% of the proceeds.
Any attempt to do so prior to this would be fruitless. all in my opinion, of course.
BRB Price at posting:
26.5¢ Sentiment: Hold Disclosure: Held