Above is a before and after image of an example of some fantastic Tanzanian zircon material I have been working with. The clarity is generally superb (VS or better), the colour sublime (pinks and oranges), and I have been able to get rough in shapely chunks of 15ct or more at times (thanks Stone Warehouse).
Zircon is renowned for its brilliant fire (high dispersion), and with its high specific gravity (SG) of approximately 4.6 and good hardness (7.5), it tends to accumulate alongside sapphire (SG 4.0), black spinel (SG 3.6), topaz (SG 3.5) and other gems in alluvial environments. The group of gemstones above are chosen as they are typical gems found in Tasmanian streams draining granite and/or basalts (e.g. the NE of Tasmania).
I am looking to source some uncut Tasmanian (not Tanzanian) zircons in at least 5ct size from any of you fossickers out there, please contact me via the website Contact Form if you have stones available.