Costing as much as $65 per gram, saffron's price by weight is roughly the same as gold, but many people don't know about the nuanced differences between saffron varieties.

Saffron is typically sold in the form of thin threads, which are the stigmas of the saffron crocus, a purple flower with the scientific name Crocus sativus.

Each saffron crocus only produces three stigmas, and while all saffron is derived from this one type of flower, each stigma comprises a range of saffron varieties.

The stigmas are divided into four different types. Pushal is the cheapest variety of saffron with the least intense flavor, comprising the yellow and orange portions of the stigma.

Sargol is saffron that comes from the very tip of the stigma. It has a strong aroma but includes some small crumbs, and because it is so fragile, the threads tend to break.

Negin, meaning 'jewel' in Farsi, is the stigma strand extending from the pushal to just below the sargol. It uses the aromatic red portion with some orange and yellow segments.

Super Negin consists of stigmas that have been precisely trimmed to include only the most potent red portion. It is the most expensive and rare variety, highly prized by chefs.

The International Organization for Standardization (ISO) grades saffron quality according to the chemicals crocin, picrocrocin, and safranal, which affect color, taste, and smell.

Laboratory tests use these three traits to assign a grade of I, II, III, or IV. Negin and super negin are grade I, sargol is grade II, pushal is grade III, and bunch saffron is grade IV.