426. As regards 'iron' meaning natural truth, this is clear from the places quoted already, and from the following as well: In Ezekiel in reference to Tyre,

Tarshish was your trader because of the vastness of all your wealth - in silver, iron, tin, and lead they provided Your wares. Dan and Javan, and Meusal, exchanged wrought iron in your tradings; cassia and calamus were in your market. Ezekiel 27:12, 19.

From these verses, and from those before and after them in the same chapter, it is quite clear that celestial and spiritual riches are meant. Each commodity, and also each name mentioned there, has some specific meaning, for the Word of the Lord is spiritual and not just verbal in content.

[2] In Jeremiah,

Can one smash iron, iron from the north, and bronze? Your resources and your treasures I will give as spoil, without price, even for all your sins. Jeremiah 15:12-13.

Here 'iron' and 'bronze' stand for natural truth and good. 'That which comes from the north' means that which is sensory and natural, for natural in comparison with spiritual and celestial is as thick darkness or the north to light or the south. The natural also resembles shade, which is also the meaning here of 'Zillah' who was the mother. It is also quite plain that 'resources and treasures' are celestial and spiritual riches.

[3] In Ezekiel,

Take an iron pan and place it as an iron wall between you and the city, and set your face ¹ towards it, and let it be in a state of siege, and oppress it. Ezekiel 4:3.

Here too it is clear that 'iron' means truth. Great strength is attributed to truth because nothing is able to withstand it. This in addition is why iron, which means truth, that is, the truth of faith, is referred to as smashing and crushing to pieces, as in Daniel 2:33, 40. And in John,

He who overcomes, to him will I give power over the nations to rule ² them with an iron rod as when earthen pots are broken in pieces. Revelation 2:26-27.

In the same author,

The woman gave birth to a male child, who was to rule ² all nations with an iron rod. Revelation 12:5.

[4] The explanation appears in John that an 'iron rod' means truth which belongs to the Word of the Lord,

I saw heaven opened, when behold, a white horse! And He who sat upon it was called faithful and true, and in righteousness He judges and fights. He was clothed in a robe dipped in blood and His name is called the Word of God. From His mouth issues a sharp sword, and with it He will smite the nations, and will rule ² them with an iron rod. Revelation 19, 11, 13, 15.

Footnotes:

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.

(References: Apocalypse Explained 1145)