I am sure that your green mineral is Chloritoid (Fe, Mg, Mn)2Al4Si2O10 (OH)4.

It occurs in regionally metamorphosed pelitic sediments and schists in the biotite, garnet, and lower grade staurolite zones; in quartz-carbonate veins and other hydrothermal environments.

Please see the pictures attached for comparison.

Best regards,

Guenter Grundmann

Guenter Grundmann, I am so gratefull for your answer. I was hesitated to name it chloritoid  because I didn't see before.

It looks like it, including the hour-glass structure; the relief is hardly visible so it's better to lower the condenser lens to take full use of your microscope. A crossed-polarizer photomicrograph would also be useful, the birefringence is low and the green(-bluish) colour persists - oh, how very much I envy guys who can recognize chloritoid from that photo alone!

I agree, tabular habit

I would suggest doing some XRF and XRD analysis on it.

I have seen minerals where colour is not a good determinant eg ruby, spinel and garnet can have similar red colours. But they are different structurally and chemically different, and can be differentiated using XRF and XRD.

Additionally you could use other techniques eg XRF to narrow down the list of minerals even further. Others techniques of significance to be used include hardness testing and refractive index.

Generally you should use at least three different techniques before reaching a conclusion.

I agree with Dr.Guenter Grundmann's suggestion that it could be chloritoid just based on similarity in photographs, as I to have seen similar chloritoids under the microscope.  However, the ones which I had seen ( a few grains in single thin section) exhibit lamellar twinning (considered to be characteristic feature of chloritoid) and are pleochroic in shades of greyish green with moderately high relief  -compared to plagioclase. Of course, I am aware that minerals can not (and should not) be identified based on similarity in appearance -since it is not micropalaeontology.  Mr. 

Gamal Abdelhamid Ahmed could have described important optical properties of the minerals he has shown in the photograph.  EPMA or XRD (of separated grains) will help in identification/confirmation.  I do not think XRF  will be useful unless one has 99.9% pure fraction of the mineral.  The whole rock analyses by XRF does not lead anywhere in identifying the constituent mineral(s).   K.N. RAO