The quartz is usually the least valuable gem... but if you are thinking in a precious gems sense... I believe that cubic zirconium would be the least valuable. even though it isn't one. This is because the diamond is the most precious, pearl the next, and i think that the birthday stones (emerald, sapphire, etc.) tie for third. Take what you want from this explanation and I hope I helped.
Gem
largest to smallest most valuable to least valuable oldest to youngest greatest to least
Small -- less than one carat, poorly cut stones with visible inclusions, are not very valuable
Whatever you have to sell is worth whatever someone will pay you for it. Best practices dictate that you take your gem to a certified gemologist who can document the characteristics of the gem. It's carat weight, its clarity, colour and cut. This professional evaluation will determine whether or not the gem has been treated or otherwise altered from its natural state, which would devalue the gem. A natural black diamond of this size will be exceedingly rare and costly. You may own a carbonado gem, which would be more common and less valuable.
There is nothing called a "gold" "gem". Something is either made of gold or it is a gem, but it is not both.
A valuable rock is a gem.
diamonds
Gem
ruby!
The Kohinoor
Red.
Yes, if it is a gem-stone quality diamond.
gems
By weight, a gem-stone quality diamond is more valuable than oil.
Of equal weight, gem-quality diamond is more valuable than silver.
composite volcanoes and ocean waves.
You must have at least 1 gem and you can gem an ability at the start of the run, you can see the abilities you can gem at the left side of the screen.