Ask Mr. Smarty Plants

From your description I keep coming back to Gentiana calycosa (Rainier pleated gentian) which I know is also called bog gentian (or mountain bog gentian) or explorer's gentian and I think you have ruled that one out.  Here are some other possibilities based on your description: 

• Gentiana parryi (Parry's gentian) looks similar and another name for it is mountain gentian.  The USDA Plants Database distribution map doesn't show it occurring in Montana but it does occur in Wyoming.
• Gentianella amarella (Autumn dwarf gentian) looks promising, except for the pointed petals.  Here are more photos.
• Penstemon albertinus (Alberta beardtongue) has some similarity to the flowers you name.  Here are more photos.   
• Phacelia linearis (Threadleaf phacelia) and here are more photos.
• Mertensia alpina (Alpine bluebells), but it has alternate leaves.  Here are more photos.
• Veronica cusickii (Cusick's speedwell) has the right color flower, but it only has 4 petals, with one large one that is a fusion of two petals.  Here are more photos and information.
• Veronica wormskjoldii (Alpine speedwell) is another possibility that also has only 4 petals.  Here are more photos and information.
• Polemonium pulcherrimum (Jacob's-ladder) and Polemonium occidentale (Western polemonium) both have flowers that sound like the one you saw.  Their leaf structure does not look like your description, however.  Here are more photos of P. pulcherrimim and for P. occidentale.
• Campanula parryi (Parry's bellflower) and here are more photos and information.

You might like to look through the following plant databases:  Montana Plant Life, Montana Field Guides, and Idaho Mountain Wildflowers.  You can do a COMBINATION SEARCH in our Native Plant Database by choosing "Montana" from Select State or Province, "Herb" from Habit (general appearance), and under Bloom Characteristics: Color select "Blue", "Purple" and "Violet".

Sorry, but we no longer accept photos of plants for identification.  We were overwhelmed with photos and didn't have enough staff and volunteers to do the research to identify the plants in the photos.  As you can read on our Plant Identification page: 

"We would love to spend all day identifying native plants for you folks! However, we already spend all day (and most of the night) answering your native plant questions. Luckily, there are some excellent forums available to help you identify those mysterious unknowns."

You can send your photos for identification to one of the links for the plant identification forums found on our Plant Identification page.

We would be very pleased to know if your unknown flower is one of the suggested ones above.