Bixbyite, (Mn,Fe)2O3, is a mixed manganese/iron oxide.
A crystal structure is a repeating pattern of where atoms go. Each site is usually occupied by a specific element, but sometimes one element can stand in for another if they are chemically similar. For example, in Bixbyite, while oxygen sites are only occupied by oxygen, metal sites are randomly occupied by either manganese or iron.
In short: Bixbyite doesn’t discriminate.
7:49 pm • 24 February 2013 • 51 notes
Euclase sample from Lost Hope Mine in Zimbabwe.
Euclase is a beryllium aluminum hydroxide silicate, BeAlSiO4(OH), but this intense blue comes from charge transfer bands in the iron impurities. When electrons move from an iron +2 ion to an iron +3 ion, the emitted light is this beautiful blue color.
10:27 pm • 19 February 2013 • 85 notes
Graphite (left) and diamond (right).
Each is made of only carbon, but one is soft enough to smear on paper, and the other is referred to as the hardest substance on earth. How do we get such different properties from the same element? The answer is in their crystal structures.
Graphite is made of strong sheets of carbon, but the chemical bonds between the sheets are very weak. When you make a pencil line on paper, the graphite’s sheets stay intact, but they are pulled apart from one another. Diamond is a 3-dimensional network of strong bonds, making the crystal too strong for you to slide apart on a piece of paper.
11:22 pm • 11 February 2013 • 62 notes
Placing a piece of garnet under your pillow is said to lessen the effects of depression. And when kept in a place of business is said to improve income and bring success business.
Good stone for friendships as well.
10:30 pm • 10 February 2013 • 112 notes
A protective stone with nurturing overtones. It also assists with facing fears, grief, and troubles and ultimately overcoming them.
1:12 pm • 10 February 2013 • 90 notes
Twinned fluorite from Blue Circle Mine in Scotland.
11:01 pm • 5 February 2013 • 183 notes
Calcite sample from the Smithsonian.
A crystal is twinned when it appears as two separate crystals grown together. That is, it grows in a perfectly ordered fashion in one part, and it has the same ordered pattern in the other half, just at a different angle. The line where they come together is called the twin boundary.
10:47 pm • 5 February 2013 • 53 notes
Hematite, Fe2O3, forms brittle plate-like crystals.
11:31 pm • 31 January 2013 • 76 notes