Michelle C. Tappert

Deep mantle diamonds from South Australia: A record of Pacific subduction at the Gondwanan margin

Diamonds from Jurassic kimberlites at Eurelia, South Australia, contain coexisting inclusions of ferropericlase and MgSi-perovskite that provide evidence for their deep (>670 km) lower mantle origin. Eurelia diamonds formed from mixed carbon sources, likely including subducted carbonate, as indicated by a trend toward isotopically heavy carbon compositions (δ 13 C = 0‰) and low nitrogen concentrations (

Characterizing Modern and Fossil Gymnosperm Exudates Using Micro-Fourier Transform Infrared Spectroscopy

Infrared absorption spectra of exudates from 65 species of gymnosperms were measured using micro–Fourier transform infrared (FTIR) spectroscopy. On the basis of the infrared spectra, three compositionally distinct groups of exudates can be distinguished: resins, volatile-rich resins, and gums. Resins and volatile-rich resins are mainly composed of terpenoids, whereas gums are polysaccharides. Resins and volatile-rich resins are restricted to conifers (Pinophyta). Gums, on the other hand, are produced by some conifer families including Araucariaceae and Podocarpaceae; nonconifer gymnosperms including Ginkgo (Ginkgophyta), cycads (Cycadophyta), and Welwitschia (Gnetophyta); and angiosperms. Using spectral band ratios, conifer resins can be subdivided quantitatively into two distinct resin types that reflect compositional differences in their terpenoid constituents and broadly parallel different conifer families. The first type of resin (pinaceous resin) is produced by members of Pinaceae and consists mainly of diterpenes that are based on abietane/pimarane skeletal structures. The second type (cupressaceous resin) is associated with members of the Cupressaceae, Sciadopityaceae, Araucariaceae, and Podocarpaceae and consists mainly of diterpenes that are based on the labdanoid structures. Variability within the resin spectra correlates with the number of free hydroxyl groups, and it can be used to assess the degree of resin polymerization. Volatile-rich resins are found exclusively within Pinaceae, reflecting a generally higher abundance of volatile mono- and sesquiterpenoids in resins of this family. The results of the FTIR spectroscopy have direct implications for the assessment of the fossil potential and the chemotaxonomic interpretation of modern and fossil gymnosperm exudates.

The Origin of Diamonds

Diamond, by definition, is a mineral composed exclusively of the element carbon. The carbon atoms in diamond are arranged in a dense cubic crystal structure (Fig.1-01), and it is this crystal structure that gives diamond its unusual physical and chemical properties. Diamond is the hardest known naturally occurring mineral (Moh’s hardness 10), but despite this extreme hardness, it is also a brittle material that can fracture in response to severe force. Another unusual property of diamond is its resistance to reactions with most chemical agents, which makes diamond virtually inert.

Unsupervised building extraction using remote sensing data to detect changes in land use

Building detection plays a key role in the identification of change in urban development analysis. Algorithms currently used to detect buildings focus only on that are in use, but they cannot be used to detect buildings under construction. In this paper, we present an unsupervised classification method that detects both types of buildings. This algorithm changes the traditional idea of region growth, and combines the advantages of two spectral-based analysis techniques—mean-shift clustering and neutrosophic set theory. This case study uses images collected by unmanned aerial vehicle over different time domains. The algorithm output is more accurate than the two latest object-based classification programs: Environment for Visualizing Images Feature Extraction (ENVI-EX) and Berkeley Image Segmentation (BIS). Commission error (CE), omission error (OE) and overall accuracy (OA) are used to assess the performances of different methods. The new algorithm performs well in both building detection and change detection. In building detection, it has an overall accuracy (OA) of up to 96.4168%. In change detection, the accuracy can reach 90.6045%. Experiments show that this new algorithm works well in detecting buildings that are in use and buildings under construction, which can be used to characterize urban change.

The Morphology of Diamonds

Natural diamonds occur as single crystals, as aggregates of a few crystals, or as clusters of countless small crystallites. The different morphologies (i.e. shape, size, number of crystals, etc.) reflect the growth conditions of diamond, and provide valuable information about the processes that led to diamond formation.

Inclusions in Diamonds

Diamonds frequently contain inclusions. These inclusions can alter the appearance and transparency of a diamond and are often undesired constituents in gemstone diamonds. On the other hand, the inclusions can provide insights into the origin of the diamonds. Although inclusions can be found in all morphological types of diamonds (i.e. monocrystalline, fi brous, and polycrystalline diamonds) the characteristics of the inclusions can be quite different for each diamond type. Monocrystalline and polycrystalline diamonds, for example, typically contain inclusions of other minerals, whereas fibrous diamonds usually contain inclusions of fluids.

The Surface Textures of Diamonds

Diamonds exhibit a wide range of surface textures that developed at different stages in their history. Some of the surface textures developed early and are linked to growth and resorption processes that occurred when the diamonds were residing in the Earth’s mantle. Others formed during exposure to the kimberlitic magma, and others formed on the Earth’s surface. Individual diamonds can exhibit many different types of surface textures, and the relationship between these textures can be used to reconstruct the sequence of events that have affected the diamonds since their formation.

The Colors of Diamonds

Diamond in its pure form is colorless, but natural diamonds commonly display a range of colors. Transparent colors that affect the entire diamond are usually caused by the presence of atomic or molecular impurities and imperfections (Fig. 3-01). Different body colors are linked to different impurities or imperfections, which form color centres. The body color of a diamond depends largely on the abundance of color centers and the size of the crystal. A large diamond will generally appear more intensely colored compared to a small diamond. Body colors are also influenced by the source of light. For example, diamonds in natural light may display a slightly different color than in artificial light.