I can't find a recording of the song by Utah but here's a version by Rosalie Sorrels. Sorrels did sing a one verse that was different from those on the Utah Phillips album, so I've included them at the bottom.

I did, however, find a picture of the back side of an album (click) which included the lyrics. I've typed them out as best I can and confirmed with Rosalie's singing.

According to the Discog's entry, the original has a "double-sided lyric sheet and four-page discussion of the origin and background of each track," but unfortunately not every page of that was uploaded there, so if you want Utah's full origins of the song, you'll need that record. Fortunately, someone on Discogs is selling it for as little as $4, so you can have it without too much cost.

For what it's worth, Utah credits the song as a traditional song. He only ever released it on one album, El Capitan, and the song was not included on any compilation albums.

STAR OF BANNOCK
(trad.)

Under the lamplight's flickering gleam,
In the dirt of a dance hall floor,
The beautiful Star of Bannock flies
Never to shine no more.

She had a lover so good and true
In the East that she left behind;
She came to the West like so many do
Her name and her fortune to find.

Her fortune she found on the dance hall floor
Where her beauty would turn men's heads;
She was the queen of them all,
Now the beautiful star is dead.

She was young and lighthearted, she danced and she sang.
Played the game as she knew it--square;
She trusted her friends and never did think
That a bullet would find her there.

Now many an eye with tears is filled,
And many a laugh is stilled,
For the beautiful Star of Bannock lies
In a grave on a lonesome hill.

[verses sung by Sorrels but not Phillips]
Her beauty that once was pure and sweet
Was that of a maiden new in
Now lies in the dust at the miner's feet
A beautiful star is dead