CLEVELAND WAY EARTHCACHE 7: CORNELIAN BAY EarthCache
CLEVELAND WAY EARTHCACHE 7: CORNELIAN BAY
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
One of a series of Earthcaches that can be completed by Geocachers walking the 110 mile Cleveland Way, without straying far from the path.
The co-ordinates should put you on White Nab overlooking a bay which derives its name from a type of semi-precious stone found locally. There has been a large landslip nearby and so the coast path turns inland for a stretch and it is not advisable to venture down to the bay in case there is further slippage: I didn't when I set this earthcache! More recently, however, Marion and Andrew (marions27) have told me that, although the path from Knipe Point down to the beach is closed, there is a good track down at the north side of the bay. It’s by the sewage pumping station just off the Cleveland way path. A bit of a scarmble at the bottom, but no difficulty at all. So if you want to get down to the beach you can!!
Cornelian is a red variety of chalcedony, which is a microcrystallized fibrous variety of quartz. Chemically, the stone is formed through a combination of the two elements which are most abundant in the earth’s crust – oxygen and silicon. The redness of cornelian is due to the presence of iron impurities in the form of iron oxide or hematite and its colour can vary from a pale flesh pink to a clear deep red.
It is formed at low temperature and often lines the cavities of volcanic rocks or the walls of metal-bearing lodes. When it has concentric zones of varying colours it is known as agate and is much valued for the making of cameos and intaglios. For these it is usually cut 'en cabochon' (into slices) but it can also be polished into round or oval beads. Imitations of cornelian are sometimes made by the staining of colourless agate.
Like all precious stones, cornelian is extremely hard and has exceptional lustre, which is linked to its refractive index of 1.543 to 1.554.
The most famous deposits are in Idar-Oberstein in Germany, which have been worked since the 15th century, but the stones were originally found in the deserts of Arabia and Egypt. Cornelian has also been found in the Rio Grande area of South America, India, China, Colombia, Saxony, Scotland & the USA.
To log this earthcache e mail me with the answers to 2 multi-choice questions.
1) The most obvious feature visible in Cornelian Bay is
a) the red colour of the rocks due to cornelian
b) a pill box
c) the layering of the rocks that make up the cliffs
d) a large cave eroded by the sea
2) On Mohs Scale of Mineral Hardness, Cornelian rates
a) 5
b) 6
c) 7
d) 8
MINERAL HARDNESS
The scale of hardness most used for materials was created by the German mineralogist Friedrich Mohs in 1812. It characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material, a method first used by Pliny the Elder around A.D. 77. On this scale, Talc is the softest with hardness 1 and Diamond the hardest at hardness 10. There is also a scale of absolute or dynamic hardness in which a scleroscope is used to measure the height of the "bounce" of a diamond-tipped hammer rebounding from the material when dropped from a fixed height. On this scale talc is still 1 but diamond is 1500.
A simple way to approximate the position of a mineral on the scale is to use ordinary materials of known hardness to see if they make a scratch.
On the Mohs scale, a pencil lead has a hardness of 1; a fingernail has hardness 2.5; a copper penny, about 3.5; a knife blade, 5.5 and a steel file has a hardness of 6.5.
Additional Hints
(Decrypt)
Or pnershy arne gur pyvssf
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures