In reply to:

There's a couple in there that aren't prepositions, specifically, but, concerning, and considering.

Faldage, your information is incomplete. True, the words but, concerning, considering do function in some sentences differently from prepositions. In numerous grammar books and dictionaries, however, but, concerning, and considering are shown as prepositions in function. It completely depends upon how the words are used in specific sentences. Check MW and you'll see.

I understand where you're coming from in that 'consider' is a verb and 'considering' is the present participle form. However, for whatever reasons of time and agreement that cause these changes in how words are categorized, the function of 'considering' in a preposition-like role in a sentence has occurred often enough that it can be parsed as a preposition. The same goes for 'concerning.' I can't say I'm happy with verbs morphing into prepositions, but apparently this categorization is not very recent. In my MW (Riverside, 1987), both participles have been so categorized. Function is all here.

'But' is easier to explain. It simply means the same as the preposition 'except' as in the sentence "Everyone but Charlie passed the test." I think the case of participles morphing into prepositions is a very interesting one. Apparently, from what I've read in my grandfather's 19th century Webster's, even 'but' itself (the preposition) was at one time a participle from some Saxon word. I would copy out the entire word history of the preposition 'but,' but it's simply too long. What is interesting is in the 19th century, before 'but' was categorized as a preposition--and I'm not speaking of the conjunction 'but' in any way--'but' was categorized as a participle! That's somehow delightful. I don't know when Webster's stopped categorizing what is now our preposition 'but' as a participle and began to name it, instead, as a preposition.

The abbreviated list of prepositions I copied out in the thread starter, by the way, comes from one of the grammar books that is used in Chesterfield County.