Please note, this Earth cache might entice you to keep some mineral samples, if you think you might want to do this a fossicking licence will be required. A simple pick or mattock would be handy but not essential. Otherwise, if you simply admire the rocks, do not do any digging and don’t keep any you will not need a licence. More information can be found HERE
Please also note the posted Coordinates are an approximate area only, your ability to get to GZ will vary with the seasons depending on the flow of the creek, as long as you can adequately touch and examine the tumbled rocks in the creek bed or edge of the creek you will be able to complete this EC.
Smoky quartz is a colour-variety of crystalline quartz. It ranges from a light yellowish brown to a brown that is so dark that it appears to be black. Low grade specimens have a greyish brown colour. When cut as a gem, stones with an orangish brown to a reddish-brown colour are preferred by many people.
Smoky quartz is a relatively inexpensive gem material because it is abundant, found in many locations, and its brown colour is not currently in high demand. It is often found in large crystals of excellent transparency with few inclusions.
The colour of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates colour centres around aluminium impurities within the crystalline quartz. Amethyst forms in a similar way, from the activation of colour centres around iron impurities.
Smoky quartz, amethyst, citrine, ametrine, rose quartz, and lemon quartz are all colour-varieties of the mineral quartz. Other than colour, they all have nearly identical properties. The properties of smoky quartz are provided in the table.
Smoky quartz is mainly found in quartz veins and pegmatite dikes that cut across igneous and metamorphic rocks. Well-formed crystals are often found in cavities of igneous and metamorphic rocks along the margins of a pegmatite. Smoky quartz formed at lower temperatures is sometimes found in fractures of sedimentary and metamorphic rocks with no known igneous association.
We had better quickly mention that Pegmatites are extreme igneous rocks that form during the final stage of a magma’s crystallization. They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks.
And a quick refresher on Metamorphic rocks, they have been modified by heat, pressure, and chemical processes, usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks.
Also, Igneous rocks, are formed from the solidification of molten rock material. Some form below Earth's surface. Some form on or above Earth's surface.
To log this Earth Cache, we require you to visit GZ and the listed waypoint to make some observations, consider the information given, then message us with the following answers to the best of your ability.
1. Find a piece of Smokey Quartz, it does not matter if its tumbled or in crystal shape. How long did it take you to find a piece? Bonus points to anyone who finds a crystal shape. We understand this task might be considered hard, we hope this is reflected adequatley in the D rating, please don't let it put you off, Smokey quartz is in an abundance in this area.
2. Describe your pieces shape and size and the properties it has; do you think it would be considered high or low grade when these properties are considered?
3. Bonus points question, can you find any other notable rocks or minerals?
4. A photo of your team or GPS nearby without giving the answers away.
You are welcome to log your find straight away to keep your TB's and Stats in order but please message us with your answers within a couple of days. Cachers who do not fulfil this Earth Cache requirement will have their logs deleted without notice.
Source: Geology.com