Spessartite, more correctly spessartine, is the manganese aluminium member of the garnet group, and it is one of the clearest examples in the atlas of a gemstone whose availability has a date.
The mineral is named after the Spessart, a range of hills in Bavaria where it was described in the early nineteenth century. For most of the time since, it was a collector's mineral: known, described, occasionally cut, and never present in the trade in any quantity. What existed was mostly small, dark and included.
That changed with two finds. Material from Namibia in the early 1990s, and then a larger and commercially decisive discovery in Nigeria later in the same decade, put clean bright orange spessartine on the market for the first time. The Namibian stones were marketed as mandarin garnet, a name that stuck and that is now applied more loosely than its origin warrants.
The consequence is that spessartine has no traditional lore at all. There is no classical attribution, no place in the navaratna, no medieval lapidary entry, because until thirty years ago there was effectively nothing to attribute anything to. Where a modern source supplies the stone with an ancient meaning, that meaning has been assigned rather than inherited, and the atlas says so.
Chemically, pure spessartine is rare; most stones sold as spessartine sit somewhere along the series toward almandine, and the orange gives way to red as the iron content rises. Colour in the garnet group tracks chemistry closely enough to be a rough analysis by eye.