Jade is a semi-precious gemstone that is classified into two varieties: nephrite and jadeite. Meanwhile, jadeite is regarded for its transparent qualities and comes in a variety of green colors, including a highly sought-after lavender. Some of the most uncommon jadeite specimens have been characterized as "moss intertwined in melting snow." Nephrite is typically brown or black in color but can also be white or gray. The name nephrite means "kidney stone" in Greek and refers to the fact that it was once used as a medicine ball to treat kidney disease. Both varieties of jade are formed by geologic processes deep within the Earth's crust. When exposed to heat and pressure, these minerals transform into each other over time. This transformation occurs primarily where temperatures range from 100 to 600 degrees Celsius (212 to 1112 degrees Fahrenheit) and pressures reach about 50 miles (80 km) below ground. The earliest evidence of human involvement with jade has been found in China, where it was used as early as 7,000 B.C. It is believed that people began harvesting nephrite from rivers because of its valuable content of iron and potassium. In addition, they used it to make tools due to its hardness. Over time, humans learned that jade could be carved into objects that were useful for daily life. These include beads, pendants, knives, and spades.