I don't think it will be big enough and then when the flower spike is at its full height it will be very top heavy and un less you prop it up it will fall over.

I have a few hyacinth vases that I used to show my girls the bulb growth but not used them in a while.

thinking about it I have a very heavy squat flower vase. I might give it ago.

Yes that was my concern too sbgirl but it is such a beautiful old pot, like yours very heavy bottomed.I I think I will just do it otherwise I will always be wondering if..
Can you post a pic of yours if you decide to do it?

You should contact a GoY member "Balcony." This member knows everything about growing amaryllis

http://www.growsonyou.com/balcony/blog/29218-amaryllis-planting-and-care

I wouldn't risk the vase - it's designed for the relatively small hyacinth not the much larger amaryllis. You could very well walk into the room one day and find your gran's vase in pieces on the floor - because it isn't going to fall over when you're there to save it. And instead of "wondering if" you'll be left crying "if only I hadn't"