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)

3413. 'And filled them up with dust' means by means of earthly things, that is, by means of self-love and love of material gain. This is clear from the meaning of 'dust' as such, dealt with in 249. The meaning is that those who are called 'the Philistines', that is, who are not concerned with life but with doctrine, efface interior truths by means of earthly loves, which are self-love and love of gain. Because of those loves they are called 'the uncircumcised', 2039, 2049, 2056, 2632. Indeed people who are under the influence of those loves cannot avoid 'filling up the wells of Abraham with dust', that is, effacing the interior truths of the Word by means of earthly things, for there is no way in which they are able from these loves to see spiritual things, that is, things which belong to the light of truth from the Lord. In fact those loves introduce darkness, and this banishes that light, for as stated just above in 3412, as the light of truth from the Lord draws nearer, people who are concerned with doctrine alone and not with life are plunged into complete darkness and stupidity. Indeed they become like those in a rage, doing all they can to destroy truths in every way. For self-love and the love of gain are such that they do not allow any truth at all from the Divine to come anywhere near them. Nevertheless those people are able to boast of and pride themselves in the fact that they know truths; indeed they proclaim them with seeming zeal. It is however the fires of self-love and love of gain which inflame them and spur them on, and their zeal is merely the enthusiasm fired by those loves. This becomes quite clear from the fact that even though truths run counter to such persons' actual lives they are able to proclaim them with the selfsame zeal or enthusiasm. These are the earthly things which block the Word itself, the fountain of all truth.