3.6" Polished Blue Calcite Heart - Argentina

Onyx is the parallel-banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands. Onyx has parallel bands, while agate has curved bands. The colors of its bands range from black to almost every color. Specimens of onyx commonly contain bands of black or white, or both.

Onyx, as a descriptive term, has also been applied to parallel-banded varieties of alabaster, marble, calcite, obsidian, and opal, and misleadingly to materials with contorted banding, such as "cave onyx" and "Mexican onyx". Many decorative materials are also referred to as "onyx", though they are typically carbonate based minerals such as "Pakistan green onyx".

Often sold under the name blue onyx or aquamarine onyx this beautiful, marbled, blue-and-caramel stone is actually calcite and not technically an onyx. It is quarried in the high mountains of Argentina at an elevation of over 17,000 feet and used as an ornamental or decorative stone.