Zircon

Mohs scale hardness: 7,5Specific gravity: 4.6-4.7^{Elements: Zr, Hf, Y, Re}

Zircon is a common accessory to trace mineral constituent of most granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands. Zircon is rare within mafic rocks and very rare within ultramafic rocks

aside from a group of ultrapotassic intrusive rocks such as kimberlites, carbonatites, and lamprophyre, where zircon can occasionally be found as a trace mineral owing to the unusual magma genesis of these rocks. Zircon forms economic concentrations within heavy mineral sands ore deposits, within certain pegmatites, and within some rare alkaline volcanic rocks, for example the Toongi Trachyte, Dubbo, New South Wales Australia in association with the zirconium-hafnium minerals eudialyte and armstrongite.References

1. https://en.wikipedia.org

2. http://www.dakotamatrix.com/products/4611/zircon

3. https://en.wikipedia.org/wiki/Zircon

4. https://www.pinterest.com/pin/490681321872339143/