Best stones come from Russia and have rich green color (chrome diopside). Clean pieces over 5 ct. are rare. Stones are generally not treated.There is the chrome variety form Kenya and Russia.
Orginating from many places including Russia, Kenya, Sri Lanka, Italy, Canada.The chemical formula is CaMgSi2O6. Forms in the monoclinic system.Hardeness is 5.5-6.5. One perfect directional cleavage, fracture is uneven to conchoidal. You will find the "star" variety in rings. The "star" are usually a little weak and have "diffused" lines. There is the chrome variety form Kenya and Russia. The best quality is purported to be from Myanmar.
Clean pieces over 5 ct. are rare and more expensive.