Rate Rate is the change as time (t) passes. Graphs which have time as the independent variable are standard means of depicting rate. The slope of a "vs. time" graph tells the rate. Because temperature is proportional to heat in a sample of material (if it is not freezing or melting) temperature vs. time graphs are indications of energy change. Rate of heating (or cooling) r = Q÷t (Note: Here T is used to represent Temperature, whereas t is used to represent time. Be sure you keep the UPPER and lower case t's straight. )
Heating is an ancient and normally stable enhancement that permanently transforms gems. Gemologists use low, medium and high temperatures in furnaces to alter gemstone color, clarity and phenomena. Nearly all of the worldâ€™s ruby, sapphire and tanzanite owe their color and clarity to heating. Many aquamarines are also heated to eliminate traces of green and gray. For a list of stone treatments, frequency and stability of treatments, and care instructions, visit our Gemstone Enhancements and Treatments chart.