Given the porphyritic texture and pink color it's likely rhyolite but it's hard to say with just a picture. What region of the world was it found in?

In South-West Bulgaria

It has phenocrysts of quartz and feldspar in a pink aphanitic groundmass.  Could be a rhyolite or dacite.  Tertiary hypabyssal dacites have been reported in this part of the world.  See the reference below.

Zagorchev, I. 1995. Pre-Palaeogene Alpine tectonics in Southwestern Bulgaria. - Geologica Balcanica, 25, 5-6; 91-112.

It is very hard to about rock on photo only. The porphyritic texture and pink color and phenocrysts of quartz and feldspar in a pink aphanitic groundmass indicates that the rock is likely to be rhyolite. please make a slide to study under microscope.

Thank's to all of you for your answers. Rhyolite is my choice too. I know that there is dacite with Oligocene age in South-West Bulgaria , but they look very different - white to grey colored with big phenocrysts of feldspar I will post a picture.

I agree with the other reseachers. It looks like the rhyolite is weakly weathered or altered.

It looks like the rhyolite

Miroslav

I am sure we could provide you with a whole-rock XRD trace if you wised to send the most representative sample to us. Feel free to contact me by e-mail.

Best wishes

Jana 

why do yellow parts occur? Any hydrothermal alteration?

Sorry, this one looks quite obvious I was referring to the other dark samples you had for XRD analysis.

Jana

I presume that the yellowing is simply due to environmental weathering of minerals in the aphanitic groundmass but it is hard to arrive at definitive conclusions from examination of a hand sample let alone from a photo of a hand sample!

Thank you Jana

I am very pleased with the presented offer to help me. So far i recieved such offers from you and from professor Kamenov. I will try with the professor, becouse he is closer to my place of residence. Thank you very much I hope, we will have a chance to collaborate in the future. 

No problem. I am glad you have access to some extra data.

 Best wishes

Jana

Again thank's to Professor Kamenov the pertrographic expertise has shown that this spicement is actually - slight metamorphosed Biotite Granite. Prime minerals are Quartz,  Potasium Feldspar and Orthoclase.  Accessory minerals are Magnetite, Titanite, Zirconium, Anatase.