They list all the minerals it provides, right on the bag. Live bacteria has come a long way since the days of bottled Cycle.
The secret lies in rich basaltic volcanic soil which contains iron, calcium, magnesium, potassium, sulfur plus over 25 other elements to nourish your aquatic plants. Eco-Complete™ Planted Aquarium Substrate is mineralogically and biologically complete,
Basaltic rock is rich in minerals and can be high in iron. There is a guaranteed analysis of minerals along with the ppm amounts on the bag that I could write here,
but it is too time consuming and I am too lazy.
Here is something from Wikipedia
Basalt in the tops of subaerial lava flows and cinder cones will often be highly vesiculated, imparting a lightweight "frothy" texture to the rock. Basaltic cinders are often red, coloured by oxidized iron from weathered iron-rich minerals such as pyroxene.
There is also a warning label on the bag that says the following:
" Eco Complete Planted aquarium Substrate is a natural product with natural variations and, as such may include a trace amount of carbonate mineral on some grain surfaces. This can temporarily raise pH and KH of the aquarium for a period of up to 3 to 6 weeks before becoming permanently neutral."
In ten years setting up over a dozen tanks, I have never had this problem. Of course this whole arguement is from another thread, but I am sure you knew that!