The unique, rich colour of Chrysoprase is caused by impurities of nickel, as this gemstone most frequently originates in nickel-rich Serpentine deposits.

Chrysoprase is cryptocrystalline, which means that it is composed of crystals so fine that they cannot be seen as distinct particles under normal magnification. This sets it apart from rock crystal, amethyst, citrine, and the other varieties of crystalline quartz. Other members of the cryptocrystalline silica family include agate, carnelian, and onyx.

Unlike many non-transparent silica minerals, it is the colour of chrysoprase, rather than any pattern of markings, that makes it desirable.

The word chrysoprase comes from the Unlike emerald which owes its green colour to the presence of chromium, the colour of chrysoprase is due to trace amounts of nickel compounds in the form of very small inclusions. The nickel reportedlyoccurs as different silicates, like kerolite or pimelite (not NiO mineral, bunsenite, as was reported before).

Chrysoprase results from the deep weathering or lateritization of nickeliferous serpentinites or other ultramafic ophiolite rocks. In the Australian deposits, chrysoprase occurs as veins and nodules with brown goethite and other iron oxides in the magnesite-rich saprolite below an iron and silica cap.