Revelation 21:21 tells us that the street of Heaven is pure gold, like transparent glass.  Gold in its purest form is transparent.  The purest form of gold is powder.  Turning that purest form back into a solid renders it clear.  Even in a liquid form, it has been said, its color is like sunshine on glass.  The Greek word for glass in Revelation 21:21 means to shine through the shadows.  Since God is light, and in Him is no darkness at all, the transparent gold of the street of heaven, will brilliantly allow the light of God to shine through!    We can only imagine how the street will shine, sparkle and lustrously glisten, especially when we think of the brilliant reflective light that comes from the prisms on very fine crystals!