Most gemstones are hard, but some soft minerals are used in
jewelry because of their lustre or other physical properties that
have aesthetic value. Rarity is another characteristic that lends
value to a gemstone.
Gemstones are formed thorough many geological processes. Some
are formed deep within the mantle and are brought to the surface by
magma movement, or are exposed through erosion and/or upliftment of
the mantle. Others are formed through the perculation of water into
rock l;ayers leading to mineralization and deposition of these
minerals. These often occur in veins. Metamorphic processes on the
rocks can also result in gemstone minerals being formed.
In this cutting (and across the road at the waypoint) you can
find evidence of small trenches being dug by
“prospectors” to remove something. In this case, they
were looking for small nodules of garnet. The garnet group includes
a group of minerals that have been used since the Bronze Age as
gemstones and abrasives. The name "garnet" may come from either the
Middle English word gernet meaning 'dark red', or the Latin
granatus ("grain"), possibly a reference to the Punica granatum
("pomegranate"), a plant with red seeds similar in shape, size, and
color to some garnet crystals. Six common species of garnet are
recognized by their chemical composition. The form found here is
most probably Almandine, a reddish to dark brownish dodecahedral
crystal. The name is a corruption of alabandicus, which is the name
applied by Pliny the Elder to a stone found or worked at Alabanda,
a town in Caria in Asia Minor. Almandine is an iron alumina garnet,
of deep red color, inclining to purple.
An Almandine crystal.
If you are lucky (I was not when I placed the cache) you will
find a small crystal. Although most are small (large grain sized) I
have found one as big as a 5 Rand coin there before.
NOTE:
= Please find a SAFE place to park your car when doing this
cache.
= Please keep children under supervision as cars can drive very
fast on this stretch of road.
= Be careful when clambering around as some of the rocks are
loose.
= Please be careful if you remove rock samples.
= I suggest bringing a hammer or small pick (geological hammer
is perfect) or trowel when doing this cache – you may be able
to loosen rocks easier.
polished
Almandine Gem ready for Jewellery.
In order to substantiate your visit and be able to claim this
Earthcache, a number of questions need to be answered and submitted
to the cache developer, via e-mail.
You should also post a photograph on the site with your log of
your GPSr near GZ.
1. Look at the rocks in the exposed cutting and describe their
shape and colour – mention things such as veins, cracks,
roughness and marked changes you may see.
2. Look for any crystals and take a photo of them and post in
your log if you are fortunate enough to find one.
3. Through which geological process do you think these gemstones
got here (deep magma; magma moving to the surface; water depositing
the minerals or metamorphic process)? What makes you choose that
answer?
4. Describe any other interesting things you saw while doing
this cache.
NOTE: You may log your visit prior to approval, but e-mail
submissions that do not meet the above criteria will be
deleted.
An example of garnet insitu (not from here :( ).
---oO0Oo---
Another in situ example of Almandine crystals (also not from
here).
