Gemstones that begin with the letter "J"

Gemstone	Crystal System	Density	Hardness	Refractive index	Treatments
Jadeite	microcrystalline	3.34	6.5-7.0	1.660-1.680	dying
Jasper	micrcrystalline	2.65	7.0	1.564-1.660	none
Jet	amorphous	1.32	2.5-4.0	1.660	none