To your questions:

I: It depends on the whole rock chemistry and mineralogy. If you have a pure limestone, your LOI would be nearly 100%. Imagine you have a carbonate-bound sandstone the LOI would be much lower. So I don't think that there is something like a standard value.

II: LOI is typically measured with temperatures up to 550, 800 or 1050°C.

III: Do you want to refer to something like a gold-carbonate?

Mr, Christian Gunther, to your answer number lll;

yes, I was referring to gold carbonaceous-sulfidic ores. What is normally LOI range value if the gold belongs to this type of ore?

Hello Syafiqah.

As per Christian, your questions is essentially "how long is a piece of string"!

There is no 'standard' LOI value for a rock. It depends entirely on the rock, and individual sample studied - even two samples from the same rock can have different LOI's.

Both carbon and sulphur will burn off in the furnace, so the answer is the more of these you have, the greater your LOI value. 

So:

i) No.

ii) LOI is checking for combustible materials such as S and C. It is usually done at the same temperature regardless of material, around 1000C.

iii) No. Having carbon present at every single point of your SEM/EDX analysis means that you carbon coated your sample before putting it into the SEM. Xray techniques are also really bad for low atomic number elements. Consult your lab manager for further details :)

I hope that helps!

standard temperature normally used for LOI test is different depend on rock type For example, organic matter is oxidized to carbon dioxide and ash at temperatures between ~200 and 500ºC.

Further evolution of carbon dioxide from carbonate mineral forms occurs at temperatures between approximately 700 and 900ºC