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Toughness of a Gemstone

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Usually when gemstones are defined as durable, they include two distinct traits, hardness and toughness.  These terms are not the same and people are often confused between these two.

Cleaving A Diamond

A mineral’s hardness is its ability to resist scratches or abrasions, and hardness is defined on the Moh’s Hardness Scale from 1 to 10, where diamond is the hardest of all mineral with a 10 on the extreme end.  Remember that the Moh’s Hardness Scale is a relative scale and not an absolute scale.

A Chinese Artisan Carving A Jadeite Jade Block

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 rating is usually stated as 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 direction.  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 Hematite is ‘excellent’ while its hardness is only 5.5.

Jadeite Jade and Nephrite Jade have a toughness graded as Exceptional, these two minerals are one of the toughest in the mineral kingdom.  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.

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I am a Graduate Gemologist trained at the Gemological Institute of America (GIA) in New York City, USA. I hold an MBA degree from Cranfield University, United Kingdom, and a Bachelor degree in Mathematics. My earlier profession was a banker until I found jade in Myanmar (Burma) in the early 90s. I have traveled to the fabled Hpakan Jade mines, and Mogok, the world’s famous rubies and sapphires mines in upper Burma, with my second son. Three of my children are also Graduate Gemologist, GIA, NYC and they deal in diamonds, gemstones and jade. 我是在美国纽约市的美国宝石学院(GIA)接受过培训的宝石研究学家。 我拥有英国克兰菲尔德大学的工商管理硕士学位和数学学士学位。我以前的职业是银行家,直到90年代初我在缅甸接触到玉石。我曾经和我的次子一起去过缅甸上流传说中的哈帕翡翠矿山和莫谷矿山, 莫谷矿山是世界上著名的红宝石和蓝宝石矿山。我的三个孩子都是纽约市GIA毕业的宝石研究学家, 他们专门处理钻石,宝石和玉石.