The word "diamond" derives from the Latin name adamas (genitive adamantis), which means "indomitable" and refers to the exceptional hardness of this stone. Diamond is a mineral made up of carbon (C) for 99.95% and other trace elements for the remaining percentage.

It has a density of 3.52 and its hardness (resistance that a mineral opposes to scratching) is equal to 10, which is the maximum hardness of the Mohs scale (scale used for evaluating the hardness of materials); the very high refractive index is 2.42. The diamond also has the highest luster term for transparent minerals, which is referred to as adamantine.

These cold but characteristic properties can be used to characterize the diamond, but they are not enough to describe this splendid and clear 1.59 carat crystal, extracted in Brazil,

preserved by the cut and donated to the Museum of Mineralogy by Monsignor Lavinio de 'Medici Spada. Diamonds like these are nowadays impossible to find, as the rarity in the discovery of crystals of size and quality such as those that characterize the specimen illustrated here, joins the rarity due to the fact that crystals with these characteristics are cut and used in jewelry store.

This diamond, deposited in 1852, is only one of the first among those present in the Museum of Mineralogy, which also houses a splendid iridescent diamond inside the Dactyliotheca and several specimens of ancient diamonds including a historical sample on a matrix from the Kimberley mine. (purchased by the museum on March 5, 1887 for a value of 600 marks, or 750 lire). In the museum there is also a collection of reproductions of famous diamonds.