Two types of stones EarthCache
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Have you ever wondered how stones are created? There are several
ways. At the given coordinates you can explore two of them...
Petrified wood (from the Greek root
petro meaning "rock" or "stone"; literally "wood
turned into stone") is the name given to a special type of
fossilized remains of terrestrial vegetation. It is the result of a
tree having turned completely into stone by the process of
permineralization .
All the organic materials have been replaced with minerals (mostly
a silicate, such as quartz), while retaining the original structure
of the wood. Unlike other types of fossils which are typically
impressions or compressions, petrified wood is a three dimensional
representation of the original organic material.
The petrifaction process occurs underground, when wood becomes
buried under sediment and is initially preserved due to a lack of
oxygen which inhibits aerobic decomposition.
Mineral-laden water flowing through the sediment deposits minerals
in the plant's cells and as the plant's lignin and cellulose decay,
a stone mould forms in its place.
In general, wood takes not too much to petrify. The organic matter
needs to become petrified before it decomposes completely.
Elements such as manganese, iron and copper in the water/mud during
the petrification process give petrified wood a variety of color
ranges. Pure quartz crystals are colorless, but when contaminants
are added to the process the crystals take on a yellow, red, or
other tint.
Following is a list of contaminating elements and related color
hues:
carbon - black
cobalt - green/blue
chromium - green/blue
copper - green/blue
iron oxides - red, brown, and yellow
manganese - pink/orange
manganese oxides - blackish/yellow
Petrified wood can preserve the original structure of the wood in
all its detail, down to the microscopic level. Structures such as
tree rings and the various tissues are often observed
features.
Petrified wood has a Mohs hardness of 7, the same as quartz
crystal.
The tree root you see at the coordinates it's about 3 millions
years old. This stone was found in Dolj county (Oltenia
region).
The word concretion is derived from
the Latin con meaning "together" and
crescere meaning "to grow". A concretion is a volume
of sedimentary rock in which a mineral cement fills the porosity
(i.e. the spaces between the sediment grains). Concretions are
often ovoid or spherical in shape, although irregular shapes also
occur.
Concretions form within layers of sedimentary strata that have
already been deposited. They usually form early in the burial
history of the sediment, before the rest of the sediment is
hardened into rock. This concretionary cement often makes the
concretion harder and more resistant to weathering than the host
stratum. Because of the variety of unusual shapes, sizes and
compositions, concretions have been interpreted to be dinosaur
eggs, animal and plant fossils (called pseudofossils),
extraterrestrial debris or human artifacts.
They are commonly composed of a carbonate mineral such as calcite;
an amorphous or microcrystalline form of silica such as chert,
flint, or jasper; or an iron oxide or hydroxide such as goethite
and hematite. They can also be composed of other minerals that
include dolomite, ankerite, siderite, pyrite, marcasite, barite and
gypsum. Although concretions often consist of a single dominant
mineral, other minerals can be present depending on the
environmental conditions which created them. For example, carbonate
concretions, which form in response to the reduction of sulfates by
bacteria, often contain minor percentages of pyrite. Other
concretions, which formed as a result of microbial sulfate
reduction, consist of a mixture of calcite, barite, and
pyrite.
Concretions are found in a variety of rocks, but are particularly
common in shales, siltstones, and sandstones. They often outwardly
resemble fossils or rocks that look as if they do not belong to the
stratum in which they were found. Occasionally, concretions contain
a fossil, either as its nucleus or as a component that was
incorporated during its growth but concretions are not fossils
themselves. They appear in nodular patches, concentrated along
bedding planes, protruding from weathered cliffsides, randomly
distributed over mudhills or perched on soft pedestals.
Small hematite concretions ("blueberries") have been observed on
Mars.
The Romanian translation for this type of rock is
"Trovant" . The name was introduced in 1907 by
Gheorghe Munteanu Murgoci in the study book:
"The Tertiary in Oltenia". 100.000.000 years ago the Oltenia
region was under sea waters. There was a lot of rivers springing in
the heals and mountains nearby. the rivers' waters were full of
sand and different size of rocks. The story of trovants you are
seeing in front of Geological museum strats 7 milions years ago. In
the North-West region of the Oltenia's see one old river create a
delta. The sand and stones cemented together and create the stones
you can see at the coordinates.
The coordinates are placing you in front of Geological museum. Here
you can found answer to question needed for logging this cache.
Inside museum you can find a lot of fossils or petrified organic
matter as well as minerals and rocks.
References:
Wikipedia -
Petrified wood
Wikipedia -
Concretion Trovants
Trovants - Romanian growing stones
The
forming of Trovant stone (romanian language only)
Amazing pictures -> "Romanian trovant" (blog Romanian language
only)
In order to log this cache you must:
1. send me a message that contain answer to following
questions:
A: the number of petrified tree roots
you can see in the area in front of Geological Museum
B: the number of concretion "Trovants"
stones in front of Geological Museum
C: the number of years needed for wood
to transform into stone
D: name at least three places in
Romania where trovants can be seen
E: your geocaching ID
2.(optional) upload an image of your GPS in front of geological
museum. At least one stone (your favorite) must be in the picture
too. You can be in the picture as well 
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