Limestone Characteristics
- General
Physical,
chemical, technical characteristics of limestone in general
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General,
Marble, Granite,
Limestone, sandstone,
Travertine |
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other,
bluestone, slate, onyx, engineered stone, manufacture stone, basalt,
pebbles, flagstone, lava |
| Q 2275: I read a response
on the FindStone expert forum by Dr. Hans saying that he had researched
60 limestones for an
architect for external cladding. I was wondering if you could share
which limestones came out on top. I'm considering honed limestone
counters for my house and am looking for the densest, best performing
ones. I was told French Beauharnais was a good one. Any information
would be most appreciated! Thank you, Nancy, July 22. |
| R3:
Dear Nancy, I can confirm Dr.Hans information. Your mentioned
BEAUHARNAIS (or CHASSAGNE BEAUHARNAIS) has porosity 3-15%, but absorption
about 1.5 - 2.5%. Much more dense with similar color there is CREMA
MARFIL from Spain with porosity 0.2 - 1.3 and water absorption 0.1
- 0.5%. Daniel, Slovakia |
R2:
Dear Nancy and other readers: The posting to which you are referring
was in one of the other (?trade) sections to do with supply. Many
limestones could have been used but there were strict guidelines
that I needed to follow for this type of construction (for example,
a thickness of 30mm, mechanical fixings, price, reliable availability,
and proximity to saltwater). Limestones are calcareous rocks made
up of at least 50% of carbonate mostly in the form of calcite, aragonite,
and dolomite. There are other carbonate varieties but these are not
significant in the context of building stone. As a group, these carbonate
rocks represent about one-fifth of all sedimentary rocks, occur on
all continents, and span all ages from recent to very old. Limestones
are regarded as non-clastic sedimentary rocks that can be formed from
many geological processes. They are texturally, structurally and mineralogically
extremely diverse - characteristics which reflect their derivation,
environment of deposition, and diagenetic history. Although a large
proportion of limestones are biogenic (contain fossil
material), there are also chemically deposited limestones which are
important as building stone, namely travertine.
The principal
factor which unifies these carbonate rocks is their high reactivity
to acids. Acids are a fact of life and here to stay. There
are many of them in our home and in our environment. Wine, carbonated
drinks, fruits and fruit juices, vinegar, and even some natural waters
will react with these carbonate rocks. And there is little that we
can do about it!! Many a posh resort and nice residences with originally
finely polished or honed limestone surfaces on their bartops or kitchen-tops
have discovered this.
Another key
characteristic of limestones is their softness relative to other rocks
such as granites. The softness is mainly a function of the
mineral composition. Calcite typically has a hardness of 3 on the
Mohs scale of hardness whereas dolomite and aragonite are a bit harder
(3.5 to 4). Because of this softness, it can be easily scratched by
most things in the house such as cutlery, coins, tools, keys, toys,
etc., so there should never be the expectation that nicely polished
or honed limestone surfaces are going to stay that way for ever.
A physical feature
of limestones which is important geotechnically is its intrinsic porosity.
Many limestones, particularly the biogenic ones, have a medium
to high degree of porosity. Porosities of 10-30% are not unusual in
the French limestones and the famous Australian limestone from Mt
Gambier has a porosity of 50%.
But although technically
weak and very absorbent, certain construction techniques (both old
and modern) allow them to be used successfully and effectively. In
cold climates, however, a porous limestone can suffer rapid degradation
due to freeze-thaw cycling and some protection might be required.
One important
structural aspect inherent in most limestones is the presence
of very fine, squiggly lines which are often brownish. These structures,
called stylolites, are pressure-solution features formed during the
compaction and lithification of limestones. Mostly, the brownish colour
is due to hydrated iron oxide but there can also be concentrations
of clays and/or sulphides. Because these stylolites are natural planes
of weakness and can often transmit fluids because they are not fully
closed, any expanding clays can react to fluids and physically weaken
the limestone.
A final comment is on
the observation that over the last few years or so, a number
of "marbles" have reverted to "limestones".
In the stone trade, it has been long accepted that any limestone that
can be polished can also be called a marble. If a limestone has undergone
some post-depositional (diagenetic) modifications some recrystallization
will have occurred. The crystals might still be quite small but the
crystalline minerals of the limestone will accept a polish. Because
marbles are "old hat" and limestone has become the buzzword
of many architects, there is now a strong trend to market mildly recrystallized
limestones that were once called marbles. Indeed, it is this group
that appears to be capturing a significant portion of the stone market.
Incidentally, some limestones from Oman and Saudi Arabia were seriously
considered for the external cladding as was the beige-coloured Jurastone
from Germany. (Dr. Hans), Australia |
R1:
Dear Nancy: I don't remember the posting you're mentioning. But it
doesn't matter. I'm
personally so "lukewarm" about limestone that I never made it my priority
to find out much about it. I just so happen to know that the densest
of the bunch (at least to the best of my knowledge) is the Solnhofen
stone from Germany (I'm not so sure about the spelling). About the
French one you indicate, I have not a clue.
Ciao and good luck, Maurizio, USA |
| Q 2256: We are an architectural
firm working on a project where we will be using limestone
on interior and exterior floors, and for interior and exterior walls.
Also guide me how to describe the different surfaces I want in general
terms. July 18, . |
R1:
For description of surfaces:
a) rough :- as found in blocks from the quarry
b) sawn:- as cut in a circular block saw or in a gangsaw
c) natural cleft :- as you find in natural slatestone and limestone,
or any stone which can be split into layers with chisel
d) bush hammered :-with a multi or single-pointed chisel
e) Chiselled :- with a chisel which leaves white line on hitting a
stone surface
f) flamed :-with a flaming oxy-acytelene or oxy-CNG flame
g) sand-blasted :- hitting a stone surface with high-pressure compressed
air with fine sand
h) Polished
i) honed :- semi-polished. The above are few of the stone finishes
u can ask for.
j) pitched face :- where the sawed or quarried surface is removed
leaving a rough, irregular scalloped appearance.
k) chopped :- where a Guillotine - type piece of equipment is used
to break the stone again leaving a rough rock face exposed. JVC. |
| A
2010: The information I read on this web-site explaining the use and
the definition of limestone.
with. I am not sure where you have gotten your information. I know
there is a lot research that has been done. I have a limestone
quarry and this stone is not soft and also weathers very well.
I personal know of homes and buildings that have this stone on them
and it has been there for 100 years. Tom, June 3, |
R2:
Dear Tom: In a perfect world, I would have to agree with you and
the answer given to you by JVC but we don't live in a perfect world,
do we!
Most importantly, we do not operate in an industry with any serious
rules and standards. In as much I always recognized that the
majority of the limestone on the marketplace will not create any problem,
as a professional stone restoration guy I witnessed all too many cases
in which certain limestone did represent a problem. What's worse is
that, not even in one single occasion, I was able (nor was anybody
else for that matter) to find a solution to any of those problems,
other than ripping the stone out! Some solution, uh! Not exactly what
end users have in mind, I suspect! So, we all agree that we have a
few inherently "bad" limestone. If you add to the mix the total ignorance
about stone displayed by distributors and installers then, as a professional,
I don't feel like advising anybody to go for it. Just too darn risky.
Ciao, Maurizio, USA |
| R1:
I'll have to agree with Tom. One cannot generalize about the suitability
of any generic stone type for various purposes. Especially with the
sedimentary stones that have not under gone metamorphism. I have been
working with many limestones, and several sandstones, both as a mason
and a carver for over 30 years. In the area where I live, there are
5 or 6 distinct limestones that are quarried for building stone, and
at least a dozen others which are not for various reasons. Experience
shows that the stones used are well suited to the task expected of
them. It is not an accident that limestone has been the builders choice
for many centuries in all corners of the world. It is not difficult
to quarry unlike granite and some marbles. It is relatively easy to
work, and impose a shape to. The dust created is not toxic like the
silicates in sandstone and granite. It weathers well, and is not as
hard to maintain as some other stones. No this does not describe every
limestone, but it does describe those which have been quarried for
many years, and used extensively in construction from ancient Egypt
through the magnificent cathedrals of Europe to new construction going
up throughout the world today. Would I use limestone for my kitchen
work surface? Probably not, although I know those who have and like
the result. Would I use limestone for my flooring? Probably yes, and
I have in many instances for completely happy clients. Would I use
limestone to build my house? Most definitely yes! over any other stone
available to me. Thanks for letting me vent.. JVC, USA, Expert Panelist |
| A 1954: I
am an Architect in Albany, NY. I am specifying a limestone cap for
a chimney. I need information as to the grade, color and finishes
of limestone. Also, the average thickness
of a limestone chimney cap. Thank you for your assistance. Rick, May
22, |
| R1:
Hi Rick.. What color
are you looking for? Limestone has a broad range of color from gray/buff
to cream/tan to bone white. I even have access to a pink limestone.
They will all eventually turn gray when exposed to the elements as
in this application. Thickness should be a minimum of 4 inches if
it is spanning any considerable distance. We have seen specs from
3 inches up to 12 inches for chimney caps, so the criteria for this
would be the look you want. Top surface can be flat, or with a 2 or
4 side wash (slope). Edges can be square and smooth, pitched faced,
or carved to a profile. Good Luck, JVC, USA |
| A 1927: Need information
on technical quality limestone
for outside. Marc, May 19,
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| R1: Dear Marc: So do
I ... So do I!! Ciao and good luck, Maurizio, USA |
| A 1486: I am a student
and I am doing a project on limestone
tiles. I need to know what raw materials you need to make limestone
tiles & the by-products produced from those limestone tiles Please
help if you can. Thank you for your time. Johanne, USA, March 1.
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| R2:
The raw materials you need to make limestone are at the bottom of
the sea all the debris shells, fish, sediment, H2O and just a few
million years. The by-products would lower the acid in your top soil.
John. UK, |
R1:
Dear Johanne: Thank goodness you're admittedly a student!! Let me
tell you, you still have a lot to study about!!
Limestone tiles are made with ... Ready for this? LIMESTONE!!!
In other words, limestone is quarried in blocks; the blocks are cut
into slices (slabs); the slabs are then cut into strips (12", or 16",
or 18"); the strips are then calibrated for thickness (grinding),
then honed and finished; Finally the strips are cut across to make
tiles out of them. Maurizio,
USA, |
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| A 1287: I hear from some
people that Texas (cream) limestone
won't stand up to freeze / thaw conditions as well as Indiana
limestone. Is this true? Also, which ASTM test results
do I look at to determine how well a stone will survive in my mountainous
Virginia climate. John, USA, Dec 31. Reply |
| R3: Water absorption is the most basic physical property and
also the most useful. It can also be used as a rule of thumb for freeze
/ thaw resistance - the lower the water absorption, the higher the
freeze / thaw resistance. Jim, Australia. |
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| R2: John.. Texas Creme Limestone has been used all
over the country, Canada, and over seas for more than 100 years now.
It will hold up in your climate about as well as any limestone. The
truth of the matter is that no porous stone will pass ASTM freeze-thaw
test as the testing is done on stone that is saturated with water,
which should never be the case with stone installed in a vertical
situation on a wall. If you are considering the stone for architectural
elements in a building, Texas stone will work just as well as any
other. If you are considering using the stone for flat work, ie patio
or staircase than you might run into a problem. Finally, whatever
stone you choose, please consider sealing with a good, breathable
sealer to limit the amount of moisture entering the stone. Texas cream
is softer than the Indiana stone, but it also has a warmer, distinctive
look to it that the Indiana stone does not have. JVC, USA. |
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| R1: John, while it is true that Texas Creme limestone is not
as stiff and dense as the Indiana limestone, it has been used successively
for exterior applications in many cold climate areas. What is the
application you are considering? Are you going to use the material
for flat work (Patio or stairs), unprotected wall cap, or for veneer
or other architectural features? The application would make a difference,
Also, no matter what stone you choose, plan on using a breathable
sealer to limit the amount of moisture gaining access to the stone,
as all pourous stones are susceptible to freeze thaw damage if water
is allowed to saturate the material. JVC, USA. |
A 943:
Please help me with comparing sandstones and
limestones with regards to composition and structure. Craig,
March 20, USA,
R1: I will keep it simple for you (if you want it more complicated
let me know and I will oblige!). Limestone used to be alive. Sandstone
did not. Limestone it's a sedimentary rock that derives from the decomposition
of (formerly) living organism and, because of that is mostly made of Calcium
Carbonate. That classifies it as a calcite rock Sandstone is still a sedimentary
rock that was formed by layers of sand that, somehow, sunk deep into the
belly of Mother Earth. Once there, high temperature partially melted the
sand, and high pressure bonded the components together. Since it is of
an inorganic origination, it's a silicate rock. Is that good enough for
you? Ciao, Maurizio, USA,
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