Colored gemstones such as sapphires and emeralds may have increased in popularity, but diamonds remain the favorite, and most expensive, choice for jewelry. With such never-ending demand, can supplies last? In this two-part series we’ll discuss where diamonds are found, and why soon we might not find too many more.
Diamonds are most often found in kimberlite pipes, carrot-shaped, volcanic rock formations. Diamonds started out as carbon that crystallized deep in the earth under great pressure and temperature. Volcanic activity brought the diamonds to the Earth’s surface in kimberlite magma. Kimberlite pipes are not the only sources of diamonds; the Natural Resources Canada website describes how erosion of kimberlite deposits over many years caused the released diamonds and indicator minerals. Advancing and receding glaciers dispersed and transported the eroded materials hundreds or thousands of miles away, creating alluvial deposits in which sometimes contain diamonds. However, most diamonds are found in the kimberlite itself.
Kimberlite can be identified by its bluish color but that doesn’t mean it’s easy to find. A article In Search of Diamonds: An Introduction to Kimberlite Exploration from the Geology for Investors website describes the diamond exploration process in three general stages:
Early Exploration: Miners investigate locations likely to contain kimberlite pipes, which are typically cratons, the oldest, most deeply rooted rock formations that make up the stable cores of the continents. This is because the stability of cratons keeps the narrow kimberlite pipe geometry intact. Regional sampling schemes are performed to determine a general search area, followed by till sampling programs and airborne geophysical surveys. Geologists and geochemists interpret the geochemical data to delineate a more precise search area and determine if it is diamondiferous.
Targeting: Once the best search area is found, miners need to figure out exactly where to drill. Priority areas identified during early exploration are targeted for high density sampling programs and higher resolution geophysical surveys. Exploration team members choose a list of targets that may indicate a mineral train leading back to the kimberlite.
Evaluation: Following the discovery of a kimberlite pipe, an assessment is made to confirm whether it is related to the associated mineral train; it’s possible there could be more than one source with different mineral chemistries, and kimberlites tend to occur in clusters. If mircrodiamond analysis reveals the kimberlite to be sufficiently diamondiferous, more drilling usually will be done to obtain an initial estimate of the grade.
Fortunately, the complex process of finding kimberlite may have just gotten easier. Cnet.com reports that a geologist working in Liberia has discovered that the rare Pandanus candelabrum plant seems to grow only on top of volcanic columns of kimberlite. With its spiky leaves, above-ground stilt-like roots, and height of about 32 feet, the plant is easy to spot.
Read our next post, The Diamond Shortage: The Hunt for Kimberlite and New High Quality Synthetics to get the business perspective on the potential diamond shortage.
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