Dust, in Ezekiel 26:12, signifies the lowest things which are of the sensual principle of man. They can be either good or bad, depending on the context.

In Isaiah 40:12, the dust signifies exterior or natural truths and goods of heaven and the church.

In Genesis 2:7, the dust is good, and we see some interesting nuances:

First, there's this: 'To form the man, dust from the ground' is to form his external man, which had not previously been man... (Arcana Coelestia 94)

Here, this formation of our external body and mind is a precursor, setting the stage for God to "breathe into our nostrils".

In Arcana Coelestia 1610, we find this passage, where again, dust has a good signification:

'Dust of the earth' has regard to those things that are celestial, for, as shown already, 'the earth' means the celestial aspect of love; 'dust of the sea' has regard to those things that are spiritual, for 'the sea', as has also been shown, means the spiritual aspect of love; while 'as the stars of heaven' means both but in a higher degree. And because these things cannot be numbered they therefore became common expressions to describe growth and multiplication beyond measure.

Then, in Arcana Coelestia 3707, these ideas get pulled together:

The reason the dust of the earth symbolizes goodness is that the earth, [or land,] symbolizes the Lord’s kingdom and therefore goodness, as shown just above in §3705. The dust of that land, then, means goodness, but earthly goodness, since the land symbolizes what is lowest in the Lord’s kingdom....

But there are bad connotations, too. In Micah 7:14-17, licking dust symbolizes being only sensual - bodily and external, worldly, and selfish. It's much the same in Psalms 72:9, where "Barbarians will bow down before God, and His enemies lick the dust...". See Arcana Coelestia 249, 3413 for interesting explanations of this.

(Odkazy: Apocalypse Explained 1145)

1610. That 'I will make your seed as the dust of the earth' means being multiplied beyond measure is clear without explanation. Here it is said that his seed would be made as 'the dust of the earth', in other parts of the Word as 'the dust of the sea', and in yet other parts as 'the stars of heaven'. Each of these phrases has its own particular meaning. 'Dust of the earth' has regard to those things that are celestial, for, as shown already, 'the earth' means the celestial aspect of love; 'dust of the sea' has regard to those things that are spiritual, for 'the sea', as has also been shown, means the spiritual aspect of love; while 'as the stars of heaven' means both but in a higher degree. And because these things cannot be numbered they therefore became common expressions to describe growth and multiplication beyond measure.

[2] The statement that his seed, that is, the faith that is the expression of love, or simply love, was to be multiplied beyond measure means in the highest sense the Lord, and in particular His Human Essence, for the Lord as regards the Human Essence is called 'the seed of the woman', dealt with in 256. When the Lord's Human Essence is meant, the infinite celestial and spiritual is understood by the words 'multiplied beyond measure'; but when faith that is the expression of charity, or simply charity, among the human race is meant by 'the seed', the multiplication without measure of that seed in everyone who leads a charitable life is understood. Such multiplication takes place in the next life with everyone who leads a charitable life. With him the multiplication of charity and of the faith deriving from it, together with their associated happiness, is so great that one can only describe it as being beyond measure and defying description. When the human race is meant by 'the seed', the multiplication of this in the Lord's kingdom is also beyond measure - not only from those who are inside the Church, and their children, but also from those who are outside the Church, and their children. Consequently the Lord's kingdom or heaven is boundless. That boundlessness will in the Lord's Divine mercy be spoken of elsewhere.