A Facebook Group I belong to, “New Zealand Lapidary, Rocks, Minerals, Fossils”, invited its members to submit photos each week of a stone, mineral or fossil in their collection that starts with a letter of the alphabet. The first Posts in this Series can be found here. The following are my Posts for “G” and “H”.
“G” is for “Green Hydrogrossular Garnet from Gemstone Beach”. Found on Gemstone Beach (Orepuki, Southland) early in March 2020, only a couple of hundred metres from the car-park, on the edge of the Taunoa Stream. The “grossular” part of its name is derived from the Latin word for gooseberry, because of the light-green colour of many hydrogrossular stones, like this one. White and brown are two other common colours, with other hues also known.
“H” is for “Hematite Jasper” – This is a small (3 cm long) hematite brecciated jasper stone found on Gemstone Beach, Southland, in February this year, tumble-polished in April.
Jocelyn Thornton provides an example of a similar stone from the same beach (see photo below, left) on page 36 of her booklet “Gemstones” .
The following comes from my research to try to understand more about hematite jasper: Jasper is a dense opaque microcrystalline quartz (the crystals are too tiny to be seen by the naked eye). “Jasper” is derived from the Greek word for “spotted stone”, referring to its typical multicoloured, striped, spotted or flamed appearance. Jasper can form in many colours, not just the dark red we usually associate it with. Hematite is a common iron oxide compound widely found in rocks and soils. It occurs naturally in a variety of colours – black to silver-gray, brown to reddish-brown, and red colours. So it is often hematite that also causes the reds in jasper, including the segments of colour seen in brecciated jasper and the “moss” in moss jasper and the “bubbles” in orbicular/poppy jasper (www.quartzpage.de/jasper.html). Mindat has some great photos of jasper and hematite (see photo below, right).
However, it is the silver-gray hue present in jasper that we tend to call “hematite jasper”. The polishing of the stone I found brought out the silvery-gray hematite shine as well as some green (maybe epidote?). Hematite shows only a very feeble response to a magnetic field and is not noticeably attracted to a magnet.
For the next Post in this Alphabetical Series, see here. The Series Index is here.
A Green Hydrogrossular Garnet is one of my favourite stones from all the stones my father collected from gemstone beach many, many years ago. The stone was positioned into the wet concrete of a concrete path which he constructed around our house. As a child I would sit reading on this concrete path, in a sun-warmed corner near where the coal range’s chimney was stationed. It happened that the pale green stone was right there and I could touch it and appreciate its colour and shape. Years later it was retrieved for me from the concrete and I now have it in front of me on my desk and in plain sight as I write.
Thanks for all the posts you write on the gemstones – I appreciate each one so much.