Traditional anniversary symbols are based on years married and typically only go up to 75 (most people don't live long enough to be married longer). I was interested in this question since the choral society I belong to will be celebrating its 90th anniversary. I did find a couple references on the web that 90 was diamond and emerald (but listed as a modern symbol, not traditional). For a wedding anniversary gift you could go with jewelry with diamonds and emeralds in it. For an anniversary symbol for our choral society celebration I will probably suggest "Double Sapphire" since sapphire is for 45 years (2 times 45).
The double sapphire signifies the 90th anniversary or birthday. This gemstone stands for royalty and wisdom, and it is believed to protect wearers from illness.
A 90th birthday anniversary is commonly referred to as a "90th birthday" or a "90th birthday celebration." Some people may also call it a "ninetieth birthday" or a "90th birthday milestone."
2002
The 90th Anniversary of the Royal Air Force will fall on 1st April 2008. (It was formed on 1st April 1918).
double Sapphire
red
It will be the year of the 90th Academy Awards.
90th, at 11 o'clock.
Their government. The people's republic of China. They just celebrated their 90th anniversary.
Bought one today for $1
56th wedding anniversary symbol?
Gala Paramount Pictures Celebrates 90th Anniversary with 90 Stars for 90 Years - 2002 TV was released on: USA: 14 July 2002 (Los Angeles, California)