GeologyRocks

Hi everyone,

 I went to Angel Island a few weeks ago and was wondering if anyone can help me figure out what type of rock this is...I have been searching many places, and came across this blog and thought it would be helpful. I have more, but...

 To start out with one:

This rock is dark green, has a type of reef that looks like a star 1/4 the size of a pinky. Also the rock does not have cleavage, it has fracture with fine-grained minerals. I tried using vinegar to test if the rock is fizzing, but it does not. In addition, I tried to scratch the rock on glass, yet does not. However, the rock is harder than my fingernail, but not harder than a knife blade. Adding on, there are no stripes at all, the rock is solid with no holes. I filled my bathroom sink with water and placed the rock inside the sink. Although the rock was still on the bottom of the sink, when I lifted the rock to the surface of the water, I noticed that the rock is dense. Another thing I notice about the rock when wet, is that there were some black spots. 

Thank You Very Much!!!