Hand-thrown Pottery by Emily Asenath-Smith
After an overview of single crystals, calcite and its unique optical properties and crystallization to be described and illustrated.
Hematite, Fe2O3, iron oxide is a product of corrosion. It causes decay and failure of metals exposed to moist and salty environments; a reality we drivers in the Northeast US know so very well.
Hematite is also the mineral in red iron oxide pigments, which are used in glazes and slips. The richness of the red color is an indication of particle size and crystal habit of the constituent particles; nanometer scale single crystalline particles appear bright red, while micrometer scale polycrystalline particulates appear a rich maroon.
One well characterized form of hematite is the pseudocube; it is formed due to hydrolysis of iron salts under acidic conditions. These micron-sized pseudocubes are neither single crystals, such as calcite discussed above, nor random polycrystalline aggregates. Hematite pseudocubes have a unique crystalline identity known as mosaic, wherein they are composed of small crystalline domains that are co-aligned. Such mosaic crystals have properties that are intermediate between single crystals and polycrystals.