1900 U.S. Federal Census; Montana; Granite County; S. Philipsburg City; Roll: T623_912; Page: 2A; Enumeration District: 43; Enumerated on 01 Jun 1900:

AUBUCHON, Celestin; head of household white; male; born Aug 1843; 56 years old; married; born in Canada (French); both parents born in Canada (French); immigrated to U.S. in 1880; did not become naturalized U.S. citizen; occupation: quartz miner.
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1910 U.S. Federal Census; Montana; Granite County; Philipsburg City; Roll: T624_832; Page: 3B; Enumeration District: 36; Image: 1055; Enumerated on 21 Apr 1910:

AUBUCHON, Celestin; head of household; white; male; 67 years old; married one time; born in Canada (French); both parents born in Canada (French); immigrated to U.S. in 1880; did not become naturalized U.S. citizen; occupation: miner--silver mine.
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MONTANA DEATH INDEX, 1907-2002:

AUBUCHON, Clestin (yes,it is spelled this way in the index)
Died: 06 Apr 1915 at 75 years of age
Index #: 94-14.
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I would imagine that Mr. Aubucon died in Granite County. It might be helpful if you obtain a copy of his Death Certificate. You can contact the Granite County Clerk & Recorder's office. These old documents cost about $3.00 plus postage. Go to the following Granite County link for the address. You can also contact Karen Palmer and see if she can obtain a copy of an obituary if one was published. Her email is also on this site:

http://www.rootsweb.ancestry.com/%7Emtgranit/

You might also want to contact the Granite County Museum and Cultural Center to see if they have anything that may be of interest to you. Call or write:

Granite County Museum
135 Sansome St.
Philipsburg, MT 59856
Phone: 406.858.3020

Good luck in your search. I am not related.