Serpentinite is a rock composed of one or more serpentine group minerals

Serpentinization is hydration and metamorphic transformation of ultramafic rocks, composed mainly of olivine and pyroxenes,

There are three main serpentine polymorphs—chrysotile, lizardite, and antigorite—whose stability fields are dependent on both thermodynamic and kinetic parameters

The final mineralogy depends both on rock and fluid compositions, temperature, and pressure. Antigorite forms in reactions at temperatures that can exceed 600 °C (1,112 °F) during metamorphism, and it is the serpentine group mineral stable at the highest temperatures. Lizardite and chrysotile can form at low temperatures very near the Earth's surface.

Ultimately depends on the Fe-Mg lattice diffusion in olivine temperature of serpentinization

You can refere

1. Evans, 2010, p. 879 of Geology. 

2. Serpentine and serpentinization: A link between planet formation and life in the same issue of Geology by..Othmar Müntenerin

Dear Mr. Masoud,

your description of the lithological setting is very vague. You speak of an almost identical mineralogical composition and a difference in color and denominate the rock as serpentinite. Serpentinite often shows strong textural and color differences which may simply be due to the alteration of the rock, be it hypogene or supergene. White asbestos (chrysotile) may be present as slip, cross or mass fibre. For a pecise answer you need to describe the rock section in more detail as to the different shades, the mineralogy and the texture. What is your denomination of the rock based upon ? This is in my opinion the key question.

Best regards

H.G.Dill

Thank you all

Dear Mr. Abdel azim Masoud,

I conducted some research on the Uitkomst complex in South Africa, which is an ultramafic body (possibly a satellite intrusion of the Bushveld complex). Due to the strong interaction with the country rocks the ultramafic body is in parts strongly altered. You can also find lizardite and chrysotile in the same altered rock units. The petrographic patterns investigated by transmitted-light microscopy indicate a strong disequilibrium of the coexisting phases which could lead to metastable phase assemblages. Perhaps this is also the case for the rocks you investigate.

Best Regards

I strongly agree what Prof.Dill said. Serpentinites and serpentization are a big story.

Regards

It is not unusual to find serpentinites showing different colours. Often the colour variation is due to the magnetite that is produced in varying quantities during alteration of the host rock (e.g. harzburgite). It may also be due to the type of host rock being altered and the degree of alteration. I suggest you read :

A book written by Dave O'Hanley on serpentinites, a whole issue on serpentinites in Elements vol9n2 and

Article Characterization of multiple serpentinization, Woodsreef, Ne...

The serpentine rocks are generally formed from the serpentinization process of ultramafic rocks that have different composition so its normal to find different types of serpentine rocks >Moreover, the  talc -carbonate rocks are formed by CO2 metasomatism 

Dear Mostafá: I agree with Dr. Harald Dill statement: the initial question posed is quite vague, and it also has a syntaxis error. Until better descriptions, field and hand sample pictures are included, little can be said. Regards. Sebastian.

Mostafa,

As Dr Latha says, serpentinite is a rock-type, made up dominantly of serpentine minerals. In my experience, it is absolutely normal to find serpentinite of different colours and different forms in the same outcrop or hand-specimen. This is due to the often complex history these rocks have undergone - several generations of deformation, of fluid-ingress, at different temperatures and at different stress regimes. You can often find dark-coloured serpentinite cut across by light-coloured serpentine (or often serpentine-carbonate-talc) veins, or vice-versa. There are all sorts of other minerals that go to make up serpentinite rock, other than serpentine itself (especially magnetite and carbonate, that partly control the dark-light colours in a hand-specimen).

If you mean, is it common to find two or more types of serpentine mineral (that you have identified by XRD or another suitable method) intimately intergrown in a small space, then yes, this is also common.

As the other comments say, you will need to specify more exactly what is the problem that you are trying to resolve, in order to receive more specific suggestions.

David