Gemstones that begin with the letter "M"

Gemstone	Crystal System	Density	Hardness	Refractive index	Treatments
Malachite	microcrystalline	3.95	3.5-4.0	1.660-1.910	reconstitution
Marcasite	orthorhombic	4.8-4.9	6.0-6.5	-	none
Maw Sit Sit	aggregate	2.5 - 3.5	6.0-7.0	1.52 - 1.74	none
Moldavite	amorphous	2.40	5.50	1.50	none
Moonstone	monoclinic	2.56	6.0-6.5	1.518-1.526	none
Morganite	hexagonal	2.72	7.5-8.0	1.577-1.583	radiation