{"id":3457,"featured":0,"modified":"2026-04-17 19:58:09","latitude":46.019051539169055331512936390936374664306640625,"longitude":-112.545833587646484375,"title":"BA&amp;P Trail - Granite Outcrops","subtitle":"","fullsize":"https://storyofbutte.org/files/fullsize/610ac92ee08b9d85b00274ca6d1306d3.jpg","address":"Location: Latitude 46.01910 Longitude -112.54566","all_locations":[],"zoom":16,"creator":["Larry Smith"],"description":"Butte Granite is made up of light-colored minerals (quartz and feldspars) and dark-colored minerals (biotite mica and amphibole). The crystals can be distinguished by the naked eye as they range from 1/16” to sometimes 1” in dimension. This outcrop is stained reddish-brown by the decomposition of the iron-bearing dark minerals, producing iron oxides, commonly known as “rust”. Most of the granite building stone in Butte is unweathered and does not have a reddish-brown cast. Some nearby examples of this rock used as building stone are the rock walls around houses at the corner of North Excelsior and Copper or Quartz streets. <br />\r\n<br />\r\nWalk east along the trail towards the East Ridge. The large fenced-in area behind the Anselmo mine yard is the site of the Anaconda wood works where timbers were milled for the underground mining operations.","sponsor":null,"accessinfo":"","lede":"","website":"","related_resources":[],"factoids":["Granite <br />\r\n<br />\r\nAn igneous rock (formed from melted rock, or magma) that formed deep below land surface. It cooled slowly, so the crystals had time to grow large enough to see with the naked eye, typically from 1/16” to 1” long. Interlocking light-colored minerals (quartz and feldspars) and dark-colored minerals (biotite mica and amphibole) make up the Butte Granite. The crystals can be distinguished by the naked eye as the range from 1/16” to sometimes 1” in dimension. The Butte Granite is exposed in the city of Butte and along the East Ridge, Timber Hill, and elsewhere in the area. The granite forms distinctive boulders, common on the surface from Boulder, Montana to and on both sides of I-90 from Butte to Pipestone, across Homestake Pass on I-90. <br />\r\n<br />\r\nOutcrop <br />\r\n<br />\r\nAn exposure of rock where they come to the surface in their natural occurrence, in that they have not been moved around by gravity or humans. Outcrops are expressions of the underlying bedrock in an area, however they are commonly buried by sediment at the surface."],"files":{"https://storyofbutte.org/files/fullsize/610ac92ee08b9d85b00274ca6d1306d3.jpg":{"id":5546,"mime-type":"image/jpeg","title":"Photo 1.jpg","description":"The rock you see in this outcrop is all one rock type. Fractures oriented in various directions have broken the outcrop into boulders. Don’t be deceived by the fractures! If you look closely at each boulder, the rock type is identical.","thumbnail":"https://storyofbutte.org/files/square_thumbnails/610ac92ee08b9d85b00274ca6d1306d3.jpg"}}}