Hi Sir PhilPamAndRob,

My three-year old and I were out caching in the Helsby/Frodsham area today. We don't usually attempt Earthcaches (the questions often make my brain hurt!) but the Brook Stone was so interesting we thought we'd give this one a stab today.

Here are my attempts at answering the questions...


1. What are the Height, Width and Depth of the Brook Stone?

Very approximately, about 60cm heigh, 75cm wide and 50cm deep.

2. Estimate its volume, and with an average density of 2.7 g/cm3 (2700kg/m3), calculate its mass.

Splitting the face of the stone down into an approximate rectangle and triangle, I guess it must have an area of about 3,750cm2 so that would make a volume of about 187,500 cm3. Mass would therefore be 506kg.

3. What Colour is the stone? What might give the stone this colour?

Very hard to tell today as it was wet but I guess it was a dark speckled, pinkish grey colour with the colour probably down to specific minerals, such as the potassium feldspars.

4. What type of rock is the Brook Stone, and is it Igneous, Sedimentary or Metamorphic?

I'm guessing it's granite which would make it an igneous rock. 

5. Based on the images below, is it Fine, Medium or coarse grained?

I would say it's on the coarse end of the scale, if anything.

6. Identify the local rock type in the Frodsham area. (hint : Frodsham is the start of a 34 mile trail heading south to Whitchurch)

Sandstone.

7. Briefly explain how both the erratic and local stone around Frodsham were formed.

Sandstone is formed under pressure when sedimentary grains of rock are cemented together in layers by a material such as clay filling the space between the grains. 

Granite is formed when molten rock cools slowly forming a crystaline structure.

Hope that they're good enough attempts at the questions to get credit for the find.

Thanks again for all the interesting caches you've placed in the area and your enthusiasm and support for the hobby which really comes across in your logs. It's very inspiring for a new cacher like myself and has really added to my experience of "the game" so far.

Best wishes,

Gareth / StridentUK