I gifted 50 polished stones found on Kai Iwi Beach, near Whanganui, to Cam who sold me some books at a good price. Many of the stones I gave to Cam are some variety of quartz, the predominant type of stone on Kai Iwi Beach. Part One describes the background and the first ten stones. This Post describes another ten of these stones.
Stone 11 again consists primarily of quartz, with only a light sprinking of iron oxide in it. You can’t see many quartz crystals in it due to their tiny size and tight compaction:
By contrast, Stone 12, another quartz, has hardly any iron oxide in it and some small clear quartz crystals are much more obvious in it:
In Stone 13, the iron oxide is laid down across only part of the stone so that where it is absent appears as white bands of varying width:
Stone 14 is what I call a “two-sider” – the two sides differ enough from each other that you could be forgiven for thinking they might belong to two different stones. The main difference is the absence or presence of yellow:
I am not sure what type of stone is Stone 15. It’s not the usual iron oxide-stained quartz. It contains a mineral that gives it a green hue, and the rectangular-like crystals in it are probably not quartz but are more likely plagioclase feldspar, another very common rock-forming mineral:
Stone 16 is a small dark red jasper. Jasper is a type of chalcedony or microcrystalline quartz, a dense aggregate of microscopic quartz crystals too small to be seen with the naked eye. It is opaque due to the presence of minerals which give it colour, with the red of iron oxide being most common. Jasper is usually classified as sedimentary, precipitating from solutions moving through the ground.
The stone could be called a “brecciated” jasper, having been fragmented to some extent by tectonic stress. The small areas between the fragments have become veins as they have been filled by mineral. The larger veins contain some white quartz, stained yellow/orange. The many fine veins in the stone have been filled with a clear mineral which could, again, be quartz. “Brecciation” has previously been explained in relation to Stone 2 (see Part One).
Stone 17 is a white quartz – you can see tiny clear crystals in the close-up photos which are embedded in a “frothy” white quartz mix, likely to contain water and/or air:
It is similar to Stone 12 (above, earlier in this Post) but the shape and distribution of the tiny clear crystals is a bit different.
Stone 18 has some similarities to Stones 4 and 9 (see Part One), consisting of white, yellow, brown and black crystals:
The white is quartz, the yellow and brown is iron oxide, and the black (sometimes sparkly) will be mica.
Stone 19 has an unusual black patterning on it, one that caught my eye on the beach:
Again the stone is quartz with some yellow/orange iron oxide, but I am unsure what the black mineral is.
Stone 20 is completely black:
There are a few tiny light areas on each side of the stone, hinting that it is quartz that has been flooded by a black mineral. I used photo software (Picasa 3) to lighten the close-up images to reveal some of the subtle patterns on the stone’s surface – on the left are the original images, on the right are the lightened ones:
Part Three, Stones 21 to 30, is not yet available.
