"And the twelve gates were twelve pearls; each one of the gates was a single pearl. And the street of the city was pure gold, like transparent glass." (Revelation 21:21 NASB)
How are we to understand this apparent oxymoron of the streets being described as both "pure gold" and "like transparent glass"?
First, the word translated transparent is diaphanes and its used just once in the New Testament: here. It's a compound of dia ("through") and phaino ("shine"). If it's a bad translation, it's also a common one. From what I see, the only two English words translators use are "transparent" and "clear". Only the Aramaic Bible in Plain English avoids the word altogether:
And 12 gates and 12 pearls, one to each, and everyone of the gates was of one pearl, but the street of the city of pure gold, as if there was glass in it.
(By the way, this passage suggests the Greek, and not the Aramaic, New Testament was written first. It's easy to see how someone could make sense of "transparent gold" by saying that it's like gold with glass in it, but the other direction is unlikely.)
Strictly speaking, gold like clear glass isn't an oxymoron as there's nothing contradictory about transparent gold. We don't actually observe gold like this because when God made it in Genesis 1, He made it opaque. This is a new type of gold. Given the other descriptions of twelve exotic jewels decorating the New Jerusalem and the twelve gates made of single, giant pearls, the street of transparent gold isn't out of place.
Alternatively it's possible the passage intends us to understand the street to be fashioned by a master craftsman who is able to make glass out of gold the way glass makers use opaque ingredients like quartz sand to make transparent objects. Glass was difficult to make and very expensive in ancient times, so making glass out of gold would produce an exceedingly valuable material. In this sense, John may be following Job's struggle to value wisdom in Job 28:12-19 (ESV):
“But where shall wisdom be found? And where is the place of understanding? Man does not know its worth, and it is not found in the land of the living. The deep says, ‘It is not in me,’ and the sea says, ‘It is not with me.’ It cannot be bought for gold, and silver cannot be weighed as its price. It cannot be valued in the gold of Ophir, in precious onyx or sapphire. Gold and glass cannot equal it, nor can it be exchanged for jewels of fine gold. No mention shall be made of coral or of crystal; the price of wisdom is above pearls. The topaz of Ethiopia cannot equal it, nor can it be valued in pure gold.
In Revelation, the extravagant language attempts to put a value on the new city. In the old Jerusalem (which would have been recently destroyed), the crowning glory was the temple of God. In the new city (which isn't heaven, but came from heaven to earth), the crowning glory is "the Lord God the Almighty and the Lamb." (Revelation 21:22b ESV) We aren't actually meant to put too much literal significance on the description of the city, but rather to use our imagination to conjure up a magnificence beyond what we have ever seen.
I do not believe that the explanation, "God has made a new type of gold" is sufficient. Firstly, we know that John is able to identify the material as gold, and such an identification could hardly be made if the material were transparent. Secondly, while we might think of gold as the element Au with the atomic number 79, that was not the definition of gold at that time. Something transparent could, by definition, not be gold, for then they would have no way of identifying it as gold. Similarly, "fish" in Jonah simply means "sea animal with fins and a tail" - we are wrong to read our modern scientific distinctions between fish and whales into ancient semantics. Thirdly, it says that the gold is pure. Anyone who has handled completely pure gold knows it to be far too malleable to make for useable roads.
Here, John is trying to describe something he has never seen before. Therefore John has to use whatever language he can to give us an impression of a reality which is completely foreign to the readers. It's like describing sight to a man who has been blind from birth. Gold is often used in the Bible to denote value, (as in the ubiquitous expression, "more precious than gold"). John is simply saying that even the material the roads are made of is precious and of great value. Its transparency is also simple to explain: Rev 21:23 The city had no need of the sun or of the moon to shine in it, for the glory of God illuminated it. The Lamb is its light. And the nations of those who are saved shall walk in its light, and the kings of the earth bring their glory and honor into it. The material the city is made of is transparent so that everyone in it will bask in the light of the glory of God.
It is very possible that many of the descriptions of heaven are physical, we are wrong to assume that the book of Revelation contains only descriptions that are purely symbolical. So although the nuclei of the atoms of which the roads are built may not each contain exactly 79 protons, the value of the materials will be great, and they will be very precious, allowing us to see through them and thus see God Himself.
Taken from Wikipedia:
Gold leaf can be beaten thin enough to become transparent.
This means that gold can actually be transparent. In fact, here you can see that it is used also in NASA's spacesuits to cover the helmet, as it is said:
The visor is coated with a thin layer of gold that filters out the sun's harmful rays.
According to Revelation 21:2 (KJV), new Jerusalem will come down from heaven, as it is said:
And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
In order to get on the earth from heaven, it would have to travel through space then. In a technical sense, it would be helpful to have the city of gold, in order to filter harmful radiations, while allowing the glory of God to be reflected outside of the city and at the same time letting those who are inside to look outside (if you travel through the universe, wouldn't you love to look outside at God's beautiful creation? :) )
So, for me, that would not be an oxymoron, as God considers also this kind of details when He plans things, and that is actually a smart choice (both on a technical and an aesthetic level).
It is very unlikely that the author of Revelation would be meaning that the streets of gold were actually transparent, that one could see through them. That makes little sense. The issue is most likely our translation of the word, which probably was employed only to describe the streets as impressively shiny. This in spite of the fact that the Greek word 'diaphanes' would appear to mean transparent (as "dia-" means through). This is because words are often used in ways that are different from or beyond what the word's individual parts or its origin would suggest. Another possibility is that the author made a poor choice of an adjective. Revelation is known for its relatively poor Greek.
I read a book once called ABOUT TIME by Paul Davies (ISBN 978-0-684-81822-1). Fascinating book. In it he discussed the atomical nature of gold and how it has many shells of electrons orbiting the molecules' nuclei. The outer shells are so far out that in order to orbit the nucleus they are moving at speeds approaching the speed of light. I'm not making this up- you can read about it in the above referenced book. When sunlight hits these near speed of light electrons it gives gold a unique translucence- a color like no other on earth, a transparency. I would assume the purer the gold the better the effect. And what kind of lighting will we have in heaven? Could gold be even more translucent there?
