Learn about Specific Gravity

One popular method to testing gems authenticity is specific gravity. Specific Gravity refers to the weight of the gem, relative to the weight of equal volume of water. In other words how much heavier the gem is to equal volume of water. This test is only applicable to loose gemstones & minerals. There are two different methods to testing for specific gravity:


1. The first is called the hydrostatic method, the gem is weighed first in air, and then is weight again in water. You can get the density by using the following formula, divide the loss of weight in water, by gem the weight in air.


2. The second method involves heavy liquids, or liquids with a density heavier than water. The main heavy liquids used are: bromoform either in pure form, at 2.89, or diluted with xylene; methylene iodide, which has a specific gravity at room temp of 3.32; and finally Clerici’s solution, which is a water based solution that combines thalium malonate and thallium formate. Clerici’s is known to be high toxic and dangerous in use. A saturated solution at room temp has a specific gravity of roughly 4.25; it may be diluted with water further.


Click here for Specific Gravity Chart