What does "open up a vein" mean?

Question

I found the phrase 'open up a vein of fury' in the article of today's Washington Post as shown below. > The New Year's Day suicide bombing of a church that killed 21 people has **opened up a vein** of fury among Egypt's Christians, built up over years of what they call government failure to address persistent discrimination and violence against their community. What does 'open up a vein of' mean exactly? Why should the writer use 'open up a vein of' in this particular case, instead of other expressions, for instance 'a spell of anger' or simply 'has infuriated'? Can somebody teach me?

Answer 1

I can think of this meanings of:

'open up a vein of'

In mining, digging down (or over) to a vein of ore is called opening up a vein. The miner is gaining access to a concentrated supply of the desired metal (or coal).