This is the first piece of Ruby Zoisote I have ever physically held in my hands so I don't know a whole lot about it. This one was in a bag of tumbling material we ordered from Madagascar, and was one of a number of rocks in the mixture that we would never tumble because it has a lesser hardness than everything else in the bag.
 
This is a nice chunk. It's quite hefty. A conservative estimate would put it at 100g. I don't have my scales right now. I was very skeptical of this ruby zoisite because of how green it is. In my research though, I just found an even greener, obviously dyed piece on AliExpress and I can now tell the difference. The green is too patchy to be dyed. It looks a lot like green calcite. 
 
These are much more likely to be faked in terms of the rubies within them. A great test to see if you have real ruby or not is to shine a UV light on it. The rubies will glow and the fakes won't. These rubies glow under both 365 and 395 uv lights. 
 
The black parts of this rock are hornblende, also known as schorl. This is low grade tourmaline. It sparkles in the light too. The zoisite is green and purple while the rubies are a pinker colour.
 
RRP for a rough chunk of ruby zoisote this size: £22+    TSC Price: £14