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Aragonite from Morocco.
A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The carbonate minerals all contain one or more carbonate (CO3-2) anions.
Aragonite has the same chemistry as calcite - it is calcium carbonate (CaCO3). However, aragonite has a different molecular structure - the atoms are packed differently. Different minerals having the same chemical formula are called "polymorphs" (another good example is graphite and diamond - both are carbon, C).
Unlike calcite, aragonite forms crystals in the orthorhombic class. Many aragonite crystals are acicular (needle-like) or pseudohexagonal. The latter is the result of six orthorhombic prisms growing parallel to each other. The sample seen here is a radiating cluster of pseudohexagonal, cyclic-twinned aragonite masses.
Aragonite is slightly harder than calcite, at H=3.5 to 4, occurs in many colors, and easily bubbles in acid. Aragonite is a little bit heavier than calcite, due to closer packing of atoms.
Most modern seashells and coral skeletons are composed of the aragonite. Whitish-colored lime sand beaches in the world are aragonitic. Occasionally, "whitings" are seen in shallow, warm ocean environments. Whitings (cloudy, milky seawater) turn out to have numerous tiny, hair-like needles of aragonite.
In the rock record, aragonitic or aragonite-rich sediments convert to calcite over time. Cenozoic-aged carbonate sedimentary rocks are often aragonitic. Mesozoic- and Paleozoic-aged carbonates are almost always calcitic. Many ancient fossils have had their aragonitic shells dissolved away. Ancient shells that were originally calcitic are often still well preserved.
Locality: Tazouta, southeast of Sefrou & southeast of Fez, Middle Atlas Mountains, northern Morocco
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Photo gallery of aragonite:
Als ich vor Tagen auf dieser roten Unterlage Tomaten zerschnitt, fiel mir auf, welches fotografische Potential in dem Arrangement steckte. Deshalb heute nochmal das gleiche für mein 366-Projekt.
The other day when I was cutting tomatoes on this red cutting board (with a red knife - all incidentally) I realized the photographic potential, so I did it again today for my 366 project.
I will admit I bought both these kids on the cheap in order to steal their arms for another doll -- and I can't bear to do it. The one on the left came to me near perfect she just needed to be restrung. The destitute little urchin on the right, I will give her new hairs and perhaps I might repaint her eyes, or not, I haven't decided yet.
Strobist: SB600 and Yin Yan (China Flash) to subject's left and right about a meter off the ground on tripods. Triggered by iShoot radio triggers.
I also used a polirizing filter to help with the sky color... It was mounted on my Tamron 18-270 VR lens (great for travel for obvious reasons but not sure how it performs compared to the kit lens for the D90)
*this was my favorite shot out of the whole set. I really liked the timing, sort of wish i had gotten the entire rope in the frame though.
A couple of weeks ago I went to meet my girlfriend in Paulista Av. (São Paulo, Brazil) to take some pictures of a friend of her's. After a couple of hours they left and I stayed behind to talk to this group of guys. They're part of a rope-skipping crew and were practicing that day. I thought it would be a good chance to practice since that was pretty much my first time taking pictures of people other than my friends and family.
I'd love to hear some critique on the work. I know I definetly need to work on my post processing. I've just recently started using Aperture 3 and plan on taking Lynda.com's Photoshop courses. I am looking forward to learn a lot about composition and lighting, hope you guys can help with that.
Cheers!