If you want to measure the density value, you need to use a density balance, such as a direct reading density balance, or you can use an ordinary electronic balance with a still water balance. These two scales range from thousands to tens of thousands. If necessary, I can recommend some models to you.
All gems have density values, so I won't list them for you. Please refer to national standards or jewelry books.
The drill pen is an instrument specially designed for identifying diamonds and their imitations. The highest thermal conductivity among gems is the drill pen stone. At room temperature, the thermal conductivity of diamond changes from 100W/ of type I to 2600W/ of type II A, and the second highest is corundum, which is 40W/. Synthetic moissanite, which appeared in recent years, has a high thermal conductivity, second only to diamond, and it also reacts under this instrument. Drill pens use the thermal properties of diamonds to identify diamonds and their imitations, except synthetic moissanite. The operation is convenient and the result is intuitive.
The drill pen consists of a probe and a control box. The metal tip of the probe is electrically heated. When the heated metal tip touches the diamond surface, the temperature drops obviously, and the electrothermal sensor will hum.