Posts tagged ‘Mineral’

November 1, 2010



Opal is a mineraloid (a mineral-like substance that does not demonstrate crystallinity) which is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl and basalt. The word opal comes from the Latin opalus (to see a change of color).

The water content is usually between three and ten percent, but can be as high as twenty percent. Opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common. These color variations are a function of growth size into the red and infrared wavelengths. Opal is Australia’s national gemstone.

June 24, 2010

Television Stone

The locality of Boron, California, produces a most unusual form of Ulexite. Gigantic hunks of this mineral are found in great amounts in the form of fibrous, compact veins. When polished, these specimens become the famous ‘Television Stone’ sold to amateur collectors. The optical effect exhibited by Television Stone is caused by each of its individual fibers acting as fiber-optic cables, transmitting light from one surface to the other. Since all the fibers are parallel and compacted together, any image at one surface is transmitted through each fiber to the other surface. Thus, any text or image at the bottom of a specimen appears as if it is on top.