Defining gemstones as durable include two distinct traits, hardness and toughness. These terms are not the same and people are often confused between these two.
Mohs’ Hardness Scale
The Mohs’ Hardness Scale was developed in 1822 by Frederich Mohs. This Mohs’ Hardness Scale 1 – 10 charts the relative hardness of the various minerals: Talc-1-softest to Diamond-10-hardest. Since hardness depends upon the strength of the bonds between atoms in a crystal, there can be variations in hardness depending upon the direction in which one measures this property. Diamonds (hardness 10) show a variation in hardness. The octahedral faces are harder than the cube faces, translated diamonds vary in hardness.
Fun Interesting Fact: Some diamonds are harder than other diamonds.
- The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder mineral to scratch a softer mineral.
- Absolute hardness relationship between minerals illustrated above
A mineral’s toughness is its ability to resist being fractured. Toughness means resistance to breaking, chipping or cracking in general, how well a stone holds up under mechanical stress, such as impact from a fall. Toughness Scale: Exceptional, Excellent, Good, Fair, or Poor.
Even though diamond is the hardest mineral it can chip and fracture in normal day to day wear and tear. Diamond is formed in the cubic crystal system and has 4 perfect cleavage directions. A cleavage direction is the weakness plane in the molecular crystal of a diamond. Hence, an experience diamond cutter will look for the cleavage plane to cleave a big diamond. The toughness rating of diamond is only ‘good’ while that of Jadeite Jade and Nephrite Jade have a toughness graded as Exceptional.
Jadeite Jade and Nephrite Jade have a toughness graded as Exceptional; these two minerals are one of the toughest in the mineral world. Hence, these minerals can be carved into minute details without fracturing the stone. Jadeite Jade is composed of micro-crystalline crystals that interlock with each other, making the mineral exceptionally tough. Nephrite Jade is of a fibrous nature consisting of extremely dense and compact fine-grained fibrous tremolite and actinolite mineral. Hence, jade can be sawed and carved into very delicate and extremely durable objects of art and adornment.
Fun Interesting Fact: When diamond and jade are harshly struck together, the diamond will cleave and the jade will bruise.