Natural Zircon is known for its distinctive beauty and occurrence in a broad range of colors and has sustained the interest of gemologists for years owing to its variation of specific gravity and refractive indices. But most curious and less known are the tenebrescent properties of some zircons. Also known as reversible photochromism, tenebrescence refers to the ability of minerals to change color when exposed to the natural radiation in sunlight.

sailorvick asked:

What about Vicky?! *u*

What I think of when I hear your name:
- An artist’s room, filled with half-finished paintings and splattered paint and easels
- Blackcurrant juice
- Multicoloured stars in a night sky

New cell marking technique to help understand how our brain works

Scientists from the University of Southampton have colour marked individual brain cells to help improve our understanding of how the brain works.

In neuroscience research, it is a challenge to individually label cells and to track them over space or time. Our brain has billions of cells and to be able to distinguish them at the single-cell level, and to modify their activity, is crucial to understand such a complex organ.

The new marking technique, known as multicolour RGB tracking, allows single cells to be encoded with a heritable colour mark generated by a random combination of the three basic colours (red, green and blue).

Brains are injected with a solution containing three viral vectors, each producing one fluorescent protein in each of the three colours. Each individual cell will take on a combination of the three colours to acquire a characteristic watermark. This approach allows researchers to colour code cells that would otherwise not be visible and undistinguishable from each other.

Once the cell has been marked, the mark integrates into the DNA and will be expressed forever in that cell, as well as in any daughter cells.

Dr Diego Gomez-Nicola, a Career Track Lecturer and MRC NIRG Fellow in the Centre for Biological Sciences at the University of Southampton, who led the multicolour RGB tracking research, says: “With this technique, we have proved the effective spatial and temporal tracking of neural cells, as well as the analysis of cell progeny. This innovative approach is primarily focused to improve neuroscience research, from allowing analysis of clonality to the completion of effective live imaging at the single-cell level.

“We predict that the use of multicolour RGB tracking will have an impact on how neuroscientists around the world design their experiments. It will allow them to answer questions they were unable to tackle before and contribute to the progress of understanding how our brain works.”

For the researchers, the next step is to change the physiology or identity of certain cells by driving multiple genetic modification of genes of interest with the RGB vectors. In the same way they made cells express fluorescent proteins, researchers hope they can change the cell expression of target genes, which would underpin gene therapy-based therapeutic approaches.

The research, which is published in the journal Scientific Reports, was funded by the Medical Research Council (MRC), the EU and Wessex Medical Research. The research also involved Professor Hugh Perry from the Centre for Biological Sciences at the University of Southampton and Professor Fehse and Dr Riecken from the University of Hamburg, Germany.

Sapphires occur in nearly every color in the rainbow, but red, since red being the domain of the ruby. Color varieties of sapphire are referred to as “fancy colored sapphires.” The most valuable  fancy sapphire is an orange-pink or pinkish-orange variety called “padparadscha” after the lotus blossom. Other very popular shades of fancy sapphires are yellows, bright oranges, lavenders and purples, and a bluish green color. Colorless or white sapphires are sometimes used as diamond substitutes.

Sapphire has long symbolized truth, sincerity, and faithfulness. Tradition holds that Moses was given the ten commandments on tablets of sapphire, making it the most sacred gemstone. Because sapphires represent divine favor, they were the gemstone of choice for kings and high priests. 

Shine bright like a diamond

Hard, bright, white and not a diamond. Introducing Phenakite, one of the brightest of the colorless gemstones with a hardness of 7-5 - 8, it is an exceptionally white gemstone. Its name is derived from the Greek word ‘phenakos’ meaning deceiver. A name acquired because of its close similarity to quartz, especially rock crystal. Indeed, phenakite was initially thought to be a variety of quartz, but its crystal twinning is distinct. It has also been confused with diamond, sapphire, topaz and beryl. 

Color change gemstones

Most gemstones show some color shift under different light conditions and this is always apparent when we change between incandescent, fluorescent, and daylights for photographing different kinds of gemstones. And when we visit gem shows, we always see a variety of lights that dealers use to make their gemstones look their best.  But few stones actually show a dramatic change in color as a result of exposure under different kinds of lighting environments.

The most important of these is of course alexandrite.  Chrysoberyl is the species name and alexandrite is the variety name. Alexandrite is that variety of chrysoberyl that changes color as a function of the light source; green in daylight and red under incandescent light.

Several other well known gemstones, including diasporesapphiregarnet and spinel may also change color as a function of the light source but the color change of top alexandrites is distinctive and attractive under any light conditions.

Spinel sometimes show a blue to violet color change but the change is usually weak and the stones never look like alexandrite. Occasionally, we’ll find a spinel with a strong color change and we once had one that showed and impressive change from red to blue.

Turkish diaspore is being sold under the name of Zultanite and higher quality versions of this stone shift from varying shades of green in daylight to a pinkish brown under incandescent light. 

But only sapphires and garnets can show any real resemblance to alexandrite.

Color change sapphires are basically known to occur in two types; the ones that change from blue to purple and the ones that change from green to red. The stones that change from green to red are the ones that can be confused with alexandrite and they only occur at the deposit in Songea, Tanzania. Although the daylight colors are usually somewhat muddy, they can be very red under incandescent light and do look similar to some of the alexandrites from the same country. Because of their similarity to alexandrites, they are referred to as alex type sapphires in Japan.

However, it is the color change garnets, especially the ones from Bekily in Madagascar and some of the stones from Nandagala, Tanzania and Chavia, in Kenya that most resemble alexandrite. The stones are actually a mixture of pyrope and spessartite and can show several colors depending on the light source. Although they look a lot like alexandrites they are different because they change color throughout the day. They are green or blue grey in the early morning and reddish in the late afternoon or in strong sunlight. Some of the stones are almost blue especially under fluorescent light but most of them are grey blue or green in daylight and change to red under incandescent or late afternoon light. The stones can show an excellent color change and can easily be confused with alexandrite. 

Without gemological tests, the stones can be distinguished from alexandrites by the needle like inclusions that are common in some of them or by the way the stones change color according to the time of day. Although they look like alexandrites, these garnets will appear red in the afternoon while the alexandrites remain green. Although the color change of some of these garnets is intense and equal to the color change of top quality alexandrites, they are available for a fraction of the price of alexandrites and demand for them is always strong.

Blue tourmaline (also known as Indicolite) oval weighing 3.13cts from the Malapa mine, Tanzania. The stone is perfectly fashioned and the deep slightly greenish blue color is exceptional.

Tourmaline is a gemstone noted for the large and unsurpassed range of colors in which it occurs, but blue is one of the rarest and most valuable color sought by collectors and connoisseurs throughout the world. Color of Indicolite (tourmaline) can vary from a light to a deep blue, but pure blue is extremely rare. A teal or blue-green color is most common color of Indicolite. Like most tourmaline, it is strongly pleochroic, meaning it shows different hues when viewed from different directions.