Module B Learning Outcomes summary study guide complete and verified 100%

Module B Learning Outcomes summary study guide complete and verified 100% Summarize the historical sources of diamond prior to 1867 - -Historically, diamonds were extremely rare and sourced from only a few scattered alluvial (i.e., within river gravels) localities. They were *first discovered in the Golconda Region of India* and then *subsequently in Brazil* by the 18th century. It has been supposed that a maximum 50,000 carats could have been produced annually from India before the 18th century and that the alluvial sources from Brazil did not produce large amounts. -The word diamond originates from the Greek word adamao, translating roughly to "I tame" or "I subdue". -common name of this mineral is rooted from Greek, it was actually in India where the first appreciation and mining of diamond occurred. -In ancient India, diamonds of euhedral shape (e.g., octahedrons) were the most valued. But the fire (its dispersion of light) and brilliance of diamonds was also recognized as a valuable feature. -One of the most reliable historical pieces of evidence of diamond's value during Roman times comes from the discovery of a rough diamond set in gold within the tomb of a wealthy young woman. To a lesser extent, diamond carving tools also began to be noted in Chinese literature around this time. -European history of diamonds as gemstones can be traced back as far as the 13th century where these stones started to adorn royal jewellery as symbols of power. -or several hundred years the right to wear diamonds was reserved for royalty, and it wasn't until the 17th century that non-royalty individuals started to adorn their own jewelry with diamonds. (still upper-upper class and used for power) -shift in jewellery design also occurred during this time period where diamonds (and other gemstones) became the centers of attention instead of the piece of art that they were hosted within. -diamond cutting became more important and the existing rose and table cuts w Discuss the significance of the discovery of diamonds in South Africa in 1867 - -It wasn't until the discovery of diamond bearing kimberlite at Kimberley, South Africa in 1867 and its subsequent exploitation, that diamonds more commonly came into the hands of not only royalty but also the upper class - Eventually, enough diamondiferous kimberlite pipes were discovered and mined that the middle class was also able to obtain diamonds. Originally, the discoveries in South Africa were made by individuals and mineral claims were hotly fought over. The establishment of the De Beers Consolidated Mines Ltd. in 1888 changed all these, and eventually the face of diamond mining in South Africa. Summarize how the dominance of the De Beers group has changed in the last century - -Shortly after the turn of the 20th century, the diamond industry consisted primarily of the De Beers group who were mining the large majority of diamonds from South Africa and also marketing them to the consumer. Having a single organization controlling the majority of diamond production and sales has had a profound impact on the development and evolution of the global diamond industry -The subsequent rise of competing diamond producers (Soviet Union in the 1950's, Australia in the 1980's and Canada in the 1990's) and the drive by consumers to ensure conflict-free diamonds has significantly changed the way diamonds are mined, polished, and sold. -Today, the global diamond industry has a handful of major corporate players, which means that De Beers' production contribution is now down to about 35% of the global total by value (as of ~2014). A number of government and non-government organizations now regulate the movement of diamonds, a highly valued commodity with significant liquidity, and are working to ensure the civil rights of miners. The Kimberley Process monitors the import/export activity of participating countries, keeping tabs on legitimately mined and processed diamonds. -today Debeers % 60 Cullinan Diamond - For many years, the great diamond was a symbol of the world's mightiest empire. - At 3,106 ct, today it remains the largest gem diamond ever discovered, and two of the diamonds cut from it lie at the heart of the Crown Jewels of England -Discovered around 1905 from Premier Mine -Premier mine significant because in its 100+ years of operation, has yielded more rough diamonds over 100 ct (300+) than any other single source, including more than 25% of all the 400+ ct diamonds ever discovered What was the first step taken by Asscher in transforming the rough stone into a gem? saw two visible inclusion, split the diamond into two What is the purpose of Figures 12 and 16, the plotting diagrams? shows quslity of the stone What are the physical dimensions of the Cullinan II, and how many facets does it have? 33 crown and 33 pavillion facet It measures 45.4 x 40.8 x 24.2 mm and weighs 317.40 ct What type of information do you think that Infrared and UV-Visible spectroscopy revealed to the gemologists and what did they infer from the results? type 2 diamond List the physical properties, composition, and crystal structure of diamond - -Mineralogically, diamond is pure carbon that is packed into a dense crystalline structure (3.51 g/cm3) with cubic symmetry and perfect octahedral cleavage -Chemical formula = C -Part of the isometric or cubic crystal system, meaning that each of the crystallographic axes is the same length and at 90 degrees to one another (i.e., the unit cell building blocks are simple cubes). -This arrangement has very strong covalently bonded carbon atoms in a highly symmetrical three dimensional network, which makes for an impressively hard, durable, and dense material. -This differentiates diamond from many other minerals in this aspect because ionic bonding is more common than covalent bonding in minerals. -Gemstone/mineral -Ranked at top of the Mohs hardness scale with a value of 10 has high durability, shows a high refractive index of 2.42, and exhibits great dispersion (splitting of light into the spectral colour of a rainbow) -Pure diamond is colourless -Various rare structural defects, elemental substitutions, and laboratory procedures allow diamonds to show the full range of colours found in the rainbow -Very high thermal conductance, low electrical conductance Describe the importance of electrical and thermal conductivity of diamond - Diamond shares physical characteristics for ones that apply for most minerals and gems, but has some other ones that are UNIQUE, like its thermal and electrical conductivities, two other properties along with refractive index and dispersion that are extensively used to confirm or reject an unknown material as being diamond. -Diamond has very HIGH thermal conductivity due to the covalent bonding that holds its carbon atoms together, and is three times higher than that of gold and silver, two metals known for their own high thermal conductivity. -Compared to its simulants, such as cubic zirconia or quartz, diamond's thermal conduction is a lot higher -Some simulants, like moissanite, which have similar thermal conductivities and so additional properties are required to be tested -The electrical conductivity of a diamond is not remarkable per se, however, its low electrical conductance paired with high thermal conductance is unusual. -Consequently, these properties together can also be distinctive from other materials, such as moissanite. -Diamond itself is an insulator (High resistivity) whereas some of its simulants, such as moissanite, are semiconductors and will more readily pass electricity when an electrical charge is placed across the stone in question. Describe the cleavage of diamond and its importance for diamond cutters - -Diamond has a set of IMAGINARY flat planes within its atomic structure that display perfect cleavage -Diamonds weakness is its cleavage -We describe these planes at being at [111], or a plane intersecting each of the three orthogonal axes at an equal unit of 1 away from the origin. -The shape of the intersecting planes is that of an octahedron (an eight-sided polyhedron), hence the descriptor of "octahedral" for its cleavage. -Four direction cleavage -Octahedral cleavage occurs when there are four cleavage planes in a crystal. -Diamond cutters require a good understanding of the mineral's crystallography and were its inherent weaknesses lie in order to expertly cute stones and grind the flat parts (facets) on a polished stone -Before the advent of analytical techniques using x-ray diffraction, info on the weakness of diamond were derived from observations that often came from gemstone cutters octahedral cleavage - Octahedral cleavage occurs when there are four cleavage planes in a crystal. Fluorite exhibits perfect octahedral cleavage. Octahedral cleavage is common for semiconductors. Diamond also has octahedral cleavage. Compare the composition, crystal structure, and bonding of graphite and diamond - -Graphite like diamond, is also a material composed entirely of carbon. -Graphite has significantly different crystal structure and therefore significantly different physical properties -This phenomenon of a material being of the same composition but having a different crystal structure is known as polymorphism and both diamond and graphite are polymorphs with the composition C -Carbon atoms within graphite are partially covalently bonded, but strong bonds only exist in 2-dimensional sheets. -Bonding between these sheets (ie, perpendicular to these planes) is of the Van der Waals type and are very weak. -Graphite therefore cleaves parallel to these sheets along the (001) plane. Comparing the crystal structures of diamond and graphite using the linked 3D models below, you'll notice that in diamond the C atoms are strongly bonded to each other in 3-dimensions -Each carbon atom is bonded to 4 oModule B Learning Outcomes summary study guide complete and verified 100%ther carbon atoms forming a tetrahedron. -When you rotate the crystal structure of graphite, the C-atoms are only strongly bonded to each other in 2-dimensions forming infinitely linked hexagons. -Each carbon atom is bonded to 3 other carbon atoms. -Between these planes, Van der Waals bonding occurs. Type Classification of Diamond and Crystal Chemistry - -Although gemologists and jewellers typically group diamonds based on the 4Cs, scientists classify diamonds based on crystal chemistry variations. -The first subdivision in the scientist's classification scheme is based on the amount of nitrogen (N) that has substituted into the crystal structure. Type I Diamonds, Ia, Ib - Type I diamonds have N concentrations greater than 10 ppm (and up to 3000 ppm) -Type I diamonds are further grouped into two: Type Ia where N atoms occur in aggregates within the diamond Type 1b where N in the diamond structure is dispersed (isolated single N impurities) Type Ia further divisions - Type Ia diamonds with clustered N are subdivided into: most common, yellowish Type IaA with paired N atoms Type IaB where 4 N atoms (quads) are clustered often with a vacancy (absence of atoms) at their center Type II - Type II diamonds have N less than 10 ppm (considered to be Nitrogen-free) -Type II diamonds with little to no N in their crystal structure can be subdivided into: Type IIa → boron free, whitest colour Type IIb → contain minute amounts of B, up to about 10 ppm General Type I and Type II stats (which one is most common, which is least common) (what colourModule B Learning Outcomes summary study guide complete and verified 100%s each produces) - Most diamonds (~98%) belong to the Type Ia group, those containing appreciable amounts of N that are clustered in the crystal structure. -Type Ia diamonds exhibit absorption of blue light and therefore show an overall yellow hue. -Type IIa is the next most common type of diamond (<2%). -These diamonds have no appreciable N or B substituting for carbon in the structure. -Due to a lack of impurities, these diamonds tend to show the whitest colour with little to *no absorption of light across the visible spectrum*. -*Physical deformation and resulting crystal defects* in Type IIa crystals give rise to most *pink*, purple, and brown diamonds. -Type IIb diamonds are very rare and contain minute amounts of B in the crystal structure but no appreciable N -Optically, the incorporation of boron causes most light except blue to be absorbed, impairing a blue to grey hue. -These diamonds are v rare and include specimens like the *Hope Diamond* -Type Ib diamonds are also very rare and characterized by appreciable N, but scattered about the crystal lattice. Diamonds of this type occur in a range in colours including yellow, brown, orange, and green or can be colourless. Identify the cause(s) of different colours of diamond - -Diamonds can be found in almost all colours of the rainbow, produced naturally or generated through various treatments (usually irradiation) -Natural colour of diamond is priModule B Learning Outcomes summary study guide complete and verified 100%marily related to its classification type, and therefore the type of impurities that are present -Another important variable for generating colour in diamonds is deformation of the crystal, which results in tiny changes in the arrangement of atoms within a crystal (like the actions of bending and buckling but on an atomic scale). -Vacancies in the crystal structure are also important in generating colour and are often tied to the deformation of the crystal lattice -A vacancy is when a hole exists in the crystal lattice where there would normally be an atom -It takes very little of an impurity, cation site vacancy, or crystal defect to generate vivid colours in stones -As a result of subtle differences, not all colours have been fully explained -There are likely multiple explanations for similar colours in diamond -Not all diamonds of a particular brown hue have acquired that hue in exactly the same way Colourless Diamonds reasons - IIa, pure Best achievable is 'D' colour, theses stones command premium prices Blue to grey - Blue to grey: Type IIb, Boron, Hope Diamond is this Yellow to orange, subdued to intense, as well as almost colourless: - Type Ia, Nitrogen, Tiffany Diamond is this Pink, purple, red, cognac: - Usually Ia, colour likely from deformation of crystal structure, Rob Red and Agra Diamonds Green - natural irradiation The Dresden Green (a Type IIa diamond too Black - abundant graphite and other opaque inclusions Rarest coloured diamonds - -Of all the diamond colours, green diamonds and red diamonds are the most rare of all diamond types due to their unique conditions of formation. --Other very rare diamond "colours" include "chameleon diamonds" which change colour upon gentle heating, and are thus termed 'thermochromic'. Although it sounds spectacular, the colour changes are usually very subtle and shift between pale browns, yellows and greens. -Coloured diamonds are generally more expensive than colourless diamonds; however, weakly coloModule B Learning Outcomes summary study guide complete and verified 100%ured stones are usually less desirable than perfectly colourless diamonds - There is a bit of subjectivity and marketing skill for pricing intermediate off-colour diamonds. -Strongly coloured diamonds (of which only a dozen or so are found globally per year) on the other hand, can be extremely valuable and command top dollar per carat. -In natural stones, the best reds, blues, and greens can cost on the order of ~$1,000,000 per carat or more depending on the history of a stone. Describe the primary morphology of diamonds, and the determining factors of the morphology - The external shape (habit) of any mineral is controlled by its internal arrangement of atoms. -Carbon atoms in diamond have cubic symmetry, so the primary shapes that diamond can take must adhere to the rules dictated by this symmetry -Secondary, or modifying, shapes can change the initial shape of any mineral through processes like corrosion or abrasion -Resulting shape of natural uncut diamonds is a mixture of primary crystallographically controlleModule B Learning Outcomes summary study guide complete and verified 100%d shapes variably modified by secondary processes. -Certain morphologies can indicate specific growth environments and subsequent geological history of a partic