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Geology/unusual rock from central Montana


rose dumont wrote at 2009-07-19 04:41:19
the "dobe" diamond is a smoky quartz crystal. they can be any color from white (clear) to almost black and shades of grey and tan. they can be found in sizes from almost pin head size to as large as my thumb nail. i am not sure why they are found there but was told years ago that there is one other place in the world they are found .. but memory fails...they are actually hexagon not five sided..and they are prism shaped

memory fails as to the type of rock they are found in..but they were in the rocks when the roadway was blasted to build a military radar site at the top of the mountain years ago..

fyi...i was raised in the judith mountains and sent many hours searching for diamonds ...

hope this helps

Dave Zackus wrote at 2009-07-29 04:17:02
I have handfulls and handfulls of these little crystals. They aren't 5 sided, but 6 sided double tipped with a 6 sided center part as well. We have always called them dobe diamonds as well. I was born in Central Montana, and visit that area alot.

I don't think they are replacements. The ground is mostly granite. There are also small smokey quartz crystals less than a mile away from that spot. I have many of these "dobe diamonds" in pretty decent shape.

Maryland 'hound wrote at 2009-10-13 19:48:44
Check out the article in October issue of R&G magazine (Pg.64). Should answer most of your questions. Been there a number of times. Neat stuff!

luap wrote at 2009-10-17 02:12:43
My research of the crystals turned up the term "double terminated beta quartz". The same source said that they don't exist in the natural state. I have been there and collected these crystals in both the matrix and weathered loose ones. They range in size from micro to over an inch in diameter. Color doesn't vary much. These are quart crystals and are translucent rather than clear. Originally called "Montana Diamonds" and were traded for drinks in local bars after they were first discovered when the road was built to the top of Judith Peak.

Carla wrote at 2012-01-12 03:44:33
I have some of these smokey crystals & am also from central Montana.

My Grandmother's mother was Jesse Dumont.  Rose Dumont responded to this question.  Could you put us together?

Mark Kirkpatrick wrote at 2012-12-13 22:50:53
Those are Montana Diamonds. They are double terminated Smoky quartz crystals.

I alway go to Judith MT to sift out a few buckets of gravel to sort at my leisure.

I don't know what the matrix is as no one can tell me even when it is in their hands.

Donna wrote at 2014-08-31 22:22:34
I am from Montana. I was wondering if there is anyone that would be willing to share some of these. I was in the Judith Mountains and had no luck at intent was to share a childhood memory with my mother and son. Any assistance would be greatly appreciated!

Sleeping_Bison wrote at 2015-10-17 16:33:15
Hi Donna,

I drove up to Judith Peak recently in search of these "diamonds" and had no luck at the top where the radio tower is, but about half a mile down from the top on the left hand side (if you're driving back down) there's an area where the rocks have been blasted away and you can clearly see many small black spots in the rocks. These are the "Montana diamonds" and you can find lots of them if you look around in the loose rubble in this area. Hope this helps!


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Dr Thomas Bell


I can answer questions regarding surface earth processes and the chemical transformations that sediments and rocks undergo with burial. I can also answer questions regarding deep time, the evolution of the elements, and the last 4.5 billion years of earth history. I specialize in metallic ore forming processes, the major geologic time periods when they were produced and what they tell us about the evolution of our planet. Learn more about my professional interests at


I am a professional consulting geologist with a background in the petroleum, mining, environmental, and geotechnical industries with over 25 years of experience.

Ph.D., Geology, University of California at Berkeley, 1984 M.A., Geology, University of California at Berkeley, 1980 B.S., Geology, San Jose State University, 1978

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