Perfumery ingredients often have fascinating names, sometimes confused by different usages and this is a case in point, in this case there are three different ingredients, all fixative base notes, that are easily confused:
Benzoin, used alone, or prefixed with Sumatra, usually refers to Styrax benzoin (also called Benzoin resinoid*), whereas Benzoin Siam is usually used to refer to Styrax tonkinensis - the latter has a sweeter smell that always reminds me of cream liqueur. These two are from tropical trees.
Steffen Arctander has this to say about them (among much else):
The name Siam is attached to this type of benzoin merely because of the fact, that the merchandise is often exported via Siam (Thailand) in transit. Benzoin Siam comes in variable sizes of pebble- like, often tear-shaped pieces, hard and brittle, rarely agglutinated. The individual pieces are yellow-orange or yellowish-brown, and a characteristic feature is the almost white or cream-colored fracture. The odor is pleasant, sweet-balsamic with a distinct note of vanillin.
Benzoin Resinoid is used very extensively in perfumery, particularly in soap perfumes (see above on discoloration) where its fixative effect is much appreciated. It is generally applicable, but it has a pronounced odor-depressing effect upon the perfumes in which it is incorporated. This effect is closely connected with the fixative effect, and it is enhanced by the rich sweetness and deep balsamic notes from the resinoid. Benzoin Resinoid is occasionally adulterated with Sumatra benzoin extracts, doctored up with vanillin (see above), or it is “stretched” with Acaroid Resinoid, abietic alcohols, methyl abietate, benzyl benzoate, copaiba balsam, amyris oil, etc.The addition of smaller amounts of diethyl phthalate as a plasticizer is considered normal “for convenient handling”, and when clearly labelled so.
Storax is quite different again (though unhelpfully it is also sometimes called Styrax or Asian Styrax) and comes from a Mediterranean tree the term is rather generic but usually refers to the resin derived from Liquidambar orientalis:
There is a good Wiki article about this species that explains the various names used and their usual meanings.
American Styrax is very similar to Storax and is produced from Liquidambar styraciflua.
Here is what Steffen Arctander says about the essential oil distilled from the balsam of Liquidambar orientallis):
* I’ve written about the meanings of the various terms used to describe different extractions of natural materials in another post.