Mysterious blue orbs of K2 granite
William Wray (USA)
K2 granite is found near the base of K2, the mountain it is named after, in the Himalayas from a rarely visited site. K2, also called “Mount Goodwin Austen” is the second highest mountain in the world, rising to 8,611m (28,253 feet). K2 got its name from the British surveyor TG Montgomerie. The “K” comes from the Karakoram mountain range and the “2” means that it is the second tallest peak recorded.
K2 granite has impressive splashes of blue circles or orbs on its surface. The blue circles are azurite inside of white K2 granite rock. The white granite is fine-grained and composed of the minerals: quartz, feldspar, muscovite and biotite. The azurite stained parts of the granite, making blue dots, which range from a couple of millimetres to about two centimetres. Azurite has a relative hardness of 3.5 to 4 on the Mohs hardness scale, but assumes the hardness of the white granite, because the azurite is only a stain. The azurite formed after all the other minerals in the granite had cooled and hardened. With a hand lens or microscope, azurite spheres reveal that the azurite appears along the edges of mineral grains, in tiny fractures in the granite, and in feldspar grains.
Since azurite and white granite are rarely found together, people don’t think the blue orbs are azurite, and commonly think of it as simply a blue dye added to make the rock a novelty. Scientific tests have not been made, so the jury is still out on the blue orbs in this interesting rock. There is lively debate on mineral forums, including www.mindat.org/, about the nature of the blue orbs.
K2 granite is an excellent lapidary material. It cuts and tumbles well because of its high feldspar content, and it can be easily shaped on a diamond wheel. K2 is durable in jewellery because the feldspar has a hardness of 6. K2 granite will scratch over time and is not suitable for bracelets or rings. It is not very pricey and excellent specimens can be bought for about $30 to $40 at gem shows in the USA and other venues. K2 granite makes colorful specimens and its bright blue azurite orbs will make it a nice addition to your collection of curiosities.
About the author
William Wray is a fifth grader at Lake George Community Charter School. He is a prolific reader with a love of all things nature related — from rocks and fossils to animals and plants. He attends the Pikes Peak Pebble Pups in Lake George, Colorado and participates there as an Earth Science Scholar.
Further reading
K2 Granite: A white granite with azurite – AKA K2 Jasper. (n.d.). Retrieved from https://geology.com/gemstones/k2/.
Nicholas Varnay and K2 — The Practical Gemologist. (n.d.). Retrieved from http://www.thepracticalgemologist.com/gemstones-2/2015/5/22/pick-of-the-week-nicholas-varnay-and-k2.