what are the "silicat"-stones?

Which alpines did you use it on?

Silicate refers to quartz stones, originally granite which eventualy breaks down to sand. This is usualy associated with plants that like acid or neutral soils. The opposite is limestone for plants that need a neutral soil. Sorry, I don't know what soapstone is.

I can't find any reference to 'soapstone-sand' lots of references to soapstone being used as a kitchen work surface, bowl, sinks, carvings etc. no sand...

This is from Pure Natural Minerals website:

Soapstone (also known as steatite or soaprock) is a metamorphic rock, a talc-schist. It is largely composed of the mineral talc and is rich in magnesium. It is produced by dynamo thermal metamorphism, which occurs at the areas where tectonic plates are subducted, changing rocks by heat and pressure, with influx of fluids, but without melting. It has been a medium for carving for thousands of years

Current Uses:

In addition to soapstone’s traditional uses, it is currently used for stair treads, balusters, sills, island tops and mixing bowls. Because of its unparalleled heat retention characteristics, it is the perfect choice for cookware, cook tops, oven floors, masonry heaters and fireplace liners. After soapstone is initially heated from burning wood, pellets or coal, it slowly radiates the heat evenly for hours – even after the fire is out. Soapstone can also be used for carving and sculpture.