I’m back to uploading more of my The Hidden Land collection.
These were also taken from the Australian Museum’s collection of rocks and minerals; the handicaps and limitations of the shots are the same – behind glass cases and limited lighting. As before, this collection features rocks and minerals highlighting their unique properties and formations. I always try to take as macro a shot as I can without loosing too much information about my subjects. Some post work was needed to bring out the textures and balance the lighting – Tone Curve, Saturation and Gamma.
Best viewed larger…really
Corundum/Rudy or Saphire
Corundum is a crystalline form of aluminium oxide (Al2O3) with traces of iron, titanium and chromium.It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red, while all other colors are called sapphire.The name corundum probably derived from the Sanskrit “kuruvinda” meaning “ruby”.
Due to corundum’s hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as an abrasive, on everything from sandpaper to large machines used in machining metals, plastics and wood. Some emery is a mix of corundum and other substances, and the mix is less abrasive, with a lower average hardness near 8.0.
In addition to its hardness, corundum is unusual for its high density of 4.02 g/cm³, which is very high for a transparent mineral composed of the low atomic mass elements aluminium and oxygen.
Corundum for abrasives is mined in Zimbabwe, Russia, and India. Historically it was mined from deposits associated with dunites in North Carolina and from a nepheline syenite in Craigmont, Ontario.Emery grade corundum is found on the Greek island of Naxos and near Peekskill, New York. Abrasive corundum is synthetically manufactured from bauxite.In 1837 Gaudin made the first synthetic rubies by fusing alumina at a high temperature with a small amount of chromium as a pigment. In 1847 Ebelmen made white sapphire by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little chromium at temperatures above 2000°C. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process.The Verneuil process allows the production of flawless single-crystal sapphires, rubies and other corundum gems of much larger size than normally found in nature. It is also possible to grow gem-quality synthetic corundum by flux-growth and hydrothermal synthesis. Because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market causing a significant reduction of price in recent years. Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratch-resistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft (because of its transparency from the UV to IR), and laser components.
Info for the group Contrasting Perceptions
lush and barren, light and shadow, sheer cliffs and gentle hill