Almo Pluton granite (top half - formed about 28 million years ago) in contact with Green Creek Complex granite (bottom half - about 2.8 billion years

- Image ID: PYM5XK
William Mullins / Alamy Stock Photo
Image ID: PYM5XK
Almo Pluton granite (top half - formed about 28 million years ago) in contact with Green Creek Complex granite (bottom half - about 2.8 billion years old). The white diagonal line is a vein (thin dike) called aplite (a mixture of fine-grained quartz and feldspar).
Location: City of Rocks Natiional Reserve, Idaho