Minnesota is famous for ‘Lake Superior Agates’ (as well as its enormous iron deposits).
In fact, Moose Lake, Minnesota has dubbed itself the ‘agate capital of the world’ and Agate Days is celebrated there each year in July.
Also called volcanics, volcanic rocks can be found in many parts of the world, including the Ring of Fire that surrounds the Pacific Ocean.
Igneous rocks are one of the three main groups in standard rock classification; the other two are sedimentary rocks and metamorphic rocks.
The cooling and crystallization of magma result in the formation of igneous rocks.
Occurring as molten or partially molten, magma is a mixture of rock particles and crystals, as well as liquid and gas deposits within the Earth.
Direct evidence that a rock is of the igneous type is when it is formed directly from the cooling of materials that flow from volcanoes.This superb 2.85 ct sunstone from Sunstone Butte displays the gem’s most valued attributes: a blend of green and red bodycolor, with reflective spangles of native copper glittering in the interior. No discussion of this topic would be complete without mention of the controversy surrounding treated copper-bearing feldspar; Rossman (2011) provides a chronology.In the early 2000s, Asian treaters perfected a method of diffusing copper into pale feldspar, flooding the market with low-priced, attractive red and green gems—which destabilized the market for Oregon sunstone.Ordinarily, states with significant mineral deposits, valuable gemstones, fossils, or unusual or significant rock occurrences will designate an official state mineral, rock/stone, gemstone, fossil, or dinosaur to promote interest in the state’s natural resources, history, tourism, etc.Accordingly, such state symbols often are a valuable clue as to potential worthwhile rockhounding opportunities.
The variety that has large crystals deposited in smaller, fine-grained crystals is called porphyry.