Topaz is a silicate material of aluminium and fluorine on of the hardest naturally occurring minerals and the hardest of any silicate minerals.  Due to its hardness, transparency and variety of colours it has long been popular for jewellery.  It does have a low index of refraction which means if it is cut with large facets unlike other gems it will not sparkle.

I have been dying to try some of the Monteverde inks, the colours look interesting unfortunately they cannot be bought in my part of the world and have to be ordered from overseas.  Many American companies will ship but I would recommend looking at fountainfeder.eu.  Prices are similar to the US and though they don’t carry a huge range of colours the virtually non-existent shipping charges make them very attractive.