Gold is not transparent in the sense that light can pass through any significant thickness of it, any more so than lead, iron, or aluminum.
But using modern techniques you can electrically deposit a layer of many types of metal, such as aluminum or gold, onto glass. The deposited layer can be made so incredibly thin that there is simply not enough metal atoms in a given area to block all of the light. So you can make many metals deposited layers appear transparent.
But pure Gold has an unusual property. Pure gold is so malleable, in the sense that you can stretch it like taffy without it breaking, that it is possible for a patient gold smith without any modern electroplating equipment to simply keep hammering a sheet of gold until it's so thin that it becomes almost as thin as a electrically deposited layer. This is not possible with any other metal, AFAIK. A sheet made of any other metal would break before you can hammer it to such a thinness. This malleability made it possible for the ancients gold smith to know if you hammer pure gold for long enough, it will eventually become so thin that it is transparent.
But using modern techniques you can electrically deposit a layer of many types of metal, such as aluminum or gold, onto glass. The deposited layer can be made so incredibly thin that there is simply not enough metal atoms in a given area to block all of the light. So you can make many metals deposited layers appear transparent.
But pure Gold has an unusual property. Pure gold is so malleable, in the sense that you can stretch it like taffy without it breaking, that it is possible for a patient gold smith without any modern electroplating equipment to simply keep hammering a sheet of gold until it's so thin that it becomes almost as thin as a electrically deposited layer. This is not possible with any other metal, AFAIK. A sheet made of any other metal would break before you can hammer it to such a thinness. This malleability made it possible for the ancients gold smith to know if you hammer pure gold for long enough, it will eventually become so thin that it is transparent.
