You can add a picture of the stone by using the paper clip icon above the typing box. (just be sure you are on a desktop or laptop computer and not a mobile phone). That will help me identify the stone for you. A measurement of the stone in mm would also help greatly.
My apologies for the quality, the paper clip icon did not allow for an image of higher quality.
Gorgeous! This is an oval cut London Blue Topaz (because of the lighting it could also be regular blue topaz) in a bezel setting. I will guess from the size comparison that it is a 7 to 10 carat stone. The necklace looks to 14k gold, so the whole necklace with stone has a value of 800 to 1000 us dollars. I am sure it is priceless to you. It is okay to wear it, the topaz is not really a 'soft stone' but rather a stone with a hardness of 8 which wears well and will not scratch or dull. This is a stone, however, that does fracture with any hard impact, so just don't drop it.
Thank you so much for the information, infact the choker chain does not fit anymore and to be honest I am thinking of selling it especially now I have a price guide and accurate description information. Many thanks, ***** ***** will deliver an excellent service rating for this.