The park covering almost 2 hectares was gazetted in 1974 to conserve its unique quartz outcrops. The White Blow is the largest of several irregular masses of quartz (silicon dioxide) in the area. Standing 15 m high with a diameter of 45 m, it is an outstanding and unusual geological formation.
Quartz
Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned, distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive.
Milky quartz is the most common variety of crystalline quartz and can be found almost anywhere. The white colour may be caused by minute fluid inclusions of gas, liquid, or both, trapped during the crystal formation.
Quartz forms when molten (>400 degrees) silicon dioxide (SiO2) rises up from deep within the earths crust and cools causing it to crystallise. Generally, the molten SiO2 finds its way into cracks and crevices and crystallises as seams of quartz within rock formations. Occasionally, as in the case of The White Blow, the SiO2 pools in large faults deep under ground resulting in large quartz formations. This probably occurred millions of years ago and a number of kilometres below the earth’s surface. Over the passage of time and through the movements of the earth’s crust, the formation has been thrust to the surface. While it is likely that a lot of other material, including that which formed the mold of The White Blow were also raised to the surface, years of erosion have left the quarts formation standing alone at the top of this hill.
Moh’s Scale of Hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
The Mohs scale of mineral hardness is based on the ability of one natural sample of matter to scratch another. The samples of matter used by Mohs are all minerals. As the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. Quartz is rated as 7 on Mohs scale. The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. Therefore, diamond is 16 times harder than quartz. That being said, Quartz is the defining mineral of several scales of hardness and is rated as 100 in the absolute hardness when measured by a sclerometer. To put quartz hardness (7) into perspective hardened steel rates as 7.5-8.
Goldich Dissolution Series (Weathering)
The Goldich dissolution series is a way of predicting the relative stability or weathering rate of various minerals on the Earth's surface. S. S. Goldich came up with the series in 1938 after studying soil profiles. He found that minerals that form at higher temperatures and pressures are less stable on the surface than minerals that form at lower temperatures and pressures. Quartz is the defining mineral of this series and its weathering is assessed as Low (the lowest in the scale).
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It should now be clear how The White Blow was formed and came to be perched on the top of this hill. Considering Moh’s Scale of Hardness and Goldich Weathering Predictions, it is clear that the materiel once surrounding The White Blow has been eroded away leaving the feature. But is The White Blow completely immune to erosion? If your answer is NO, how does the quartz feature’s erosion differ from that of the material that once surrounded it?
UPDATE: Monkeys are all grown up, and I don't check in as often as I should. Feel Free to log your find.
You are not required to post a picture in order to claim this cache, but the Monkeys and I would love to see you enjoying this unique experience too, if you like.