The sailing stones are a geological phenomenon found in the Racetrack Playa located in the northern part of the Panamint Mountains in Death Valley National Park, California. The stones slowly move across the surface of the playa without human or animal intervention leaving a track as they go. They have never been seen or filmed in motion. Racetrack stones only move once every two or three years and most tracks last for just three or four years.

Stones with rough bottoms leave straight striated tracks while those with smooth bottoms wander. Stones sometimes turn over, exposing the other edge to the ground and leaving a different-sized track in the stone’s wake.

The sailing stones are most likely moved by strong winter winds of up to 90 mph. Once it has rained enough to fill the playa with just enough water to make the clay slippery, the winds push the stones across the slick surface. The prevailing winds across Racetrack Playa blow from southwest to northeast, with most of the rock trails parallel to this direction, lending support to this hypothesis.

An alternate hypothesis builds upon the first. As rain water accumulates, strong winds blow thin sheets of water quickly over the relatively flat surface of the playa. A layer of ice forms on the surface as night temperatures fall below freezing. Wind then drives these floating ice sheets, their aggregate inertia providing the necessary force required to move the larger stones.

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. It is a key mineral in interpreting the genesis of many igneous and metamorphic rocks via geothermobarometry. Diffusion of elements is relatively slow in garnet compared to rates in many other minerals, and garnets are also relatively resistant to alteration. Hence, individual garnets commonly preserve compositional zonations that are used to interpret the temperature-time histories of the rocks in which they grew. Garnet grains that lack compositional zonation commonly are interpreted as having been homogenized by diffusion, and the inferred homogenization also has implications for the history of the host rock.

Garnet sand is a good abrasive, and a common replacement for silica sand in sand blasting. Mixed with very high pressure water, garnet is used to cut steel and other materials in water jets. Garnet sand is also used for water filtration media. There are different kinds of abrasive garnets which can be divided based on their origin. The largest source of abrasive garnet today is garnet rich beach sand which is quite abundant on Indian and Australian coasts.

Rock garnet is perhaps the garnet type used for the longest period of time. This type of garnet is produced in America, China and western India. These crystals are crushed in mills and then purified by wind blowing, magnetic separation, sieving and if required, washing. Being freshly crushed, this garnet has the sharpest edges and therefore performs far better than other kinds of garnet. Both the river and the beach garnet suffer from the tumbling effect of hundreds of thousands of years which rounds off the edges.

Garnet has been mined in western Rajasthan for the past 200 years, but mainly for the gemstone grade stones. Abrasive garnet was mainly mined as a secondary product while mining for gem garnets and was used as lapping and polishing media for the glass industries.