Here is a very big Vivianite specimen from Chernomorsky Mine, Kerchenskoe Deposit, Kerch Peninsula, Crimea, Russia.
It measures 165x106x64 mm and the weight is 1233 grams.
Dark green (appears black) Vivianite crystals. Big motherstone, I only have one of these.
Please also watch the video for a better view:
My father bought this one a long time ago, probably 20-30 years ago.