It really depends on the person...diamonds are popular of course and there are sapphires, emeralds, rubies, pearls, so on so forth. Opals are very beautiful and so is topaz to me, but as I said, it depends who you are.
Diamond is the most popular gem. They vary in size and cost but this will always be the most popular gem. Behind diamonds are pearls and then semi precious stones.
Australia's most famous gem is the opal. Around 95% of the world's opals are mined in Australia.
diamonds
diamonds
Diamond.
Amethyst is the first that comes to mind (and perhaps the most popular) but you can get a variety of purple gem stones.
Not a diamond.I know that
The Kohinoor
Gem's. Gem's could also be 'gem is' so you have to note the context of the word to tell if it is possessive or 'is' eg The gem's green -- gem's = gem is The gem's colour is green. -- gem's = possessive
Most likely Opal
The most popular gem is the diamond. It is a focal point of many pieces of jewelry, even if there are other stones in the jewelry. Other popular gems stones are the pearl and emerald, and most of the other birthstones.
Sapphire