Topaz and Zircon are completely different natural gemstone. Both have different chemical, physical and optical properties.
- Natural White Topaz (http://www.gemstonebuzz.com/topaz) is an affordable substitute for Natural White Sapphire.
- Natural White Zircon (http://www.gemstonebuzz.com/zircon) is an affordable substitute for Natural White Diamond.
So, as suggested by astrologer, you will have to go with Natural White Zircon to get the benefits.
In case you are buying from eBay.in, please talk with the seller through email or phone first and read the ratings and reviews of the seller before buying.
VERY IMPORTANT: Only buy gemstone which has been certified from reputed gemological lab.