where are the largest crystals found on earth
Cave of the Crystals The main chamber contains giant selenite crystals (gypsum, CaSO4·2 H2O), some of the largest natural crystals ever found.[1] The cave's largest crystal found to date is 12 m (39 ft) in length, 4 m (13 ft) in diameter and 55 tons in weight. The cave is extremely hot, with air temperatures reaching up to 58 °C (136 °F)[2] with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors.[3] Without proper protection, people can only endure approximately ten minutes of exposure at a time.[4]
Basalt By definition, basalt is an aphanitic (fine-grained) igneous rock with generally 45-53% silica (SiO2)[2] and less than 10% feldspathoid by volume, and where at least 65% of the rock is feldspar in the form of plagioclase. This is as per definition of the International Union of Geological Sciences (IUGS) classification scheme.[3][4][5] It is the most common volcanic rock type on Earth, being a key component of oceanic crust as well as the principal volcanic rock in many mid-oceanic islands, including Iceland, the Faroe Islands, Réunion and the islands of Hawaiʻi. Basalt commonly features a very fine-grained or glassy matrix interspersed with visible mineral grains. The average density is 3.0 g/cm3.