On 28 Apr 2005 16:54:13 +0100 (BST), Theo Markettos
wrote:

andrewpreece wrote:
Sharp sand is gritty to the touch, the grains are angular, in my neck of
the woods it is a light grey colour. Builder's sand is also known as soft
sand and is usually a golden colour, soft to the touch, staining your
fingers yellow, and made up of many different sizes of rounded particle,
down to clay size. It is good for bricklaying and mortar.

Am I right in thinking that sharp sand is mostly quartz with similar grain
size (from aeolian or water deposits - think sandy beach) whilst builder's
sand is mechanically ground up rock (of any provenance) with a large
proportion of feldspar minerals which will get hydrated to clays in short
order? So in other words you're just adding more clay?

Theo

Sharp sand and builder's sand are both just natural sands from
whatever source, usually quartz as you suggest, washed and sieved to
the appropriate sizes where required.

The finer you crush rock, the more energy it takes and the more
expensive it gets. Making builder's sand that way would be very
expensive. Certainly, rock crushing to make roadstone or aggregates
for concrete generates some fine stuff, but not nearly enough for the
building industry.

Sharp sand is made up of angular grains, as Andrew says, while aeolian
sands tend to have rounded grains. In SW England, we have squillions
of tons of angular-grained sand available as a by-product from the
china clay industry. Mostly quartz, some feldspar, light grey to white
in colour. Washed and graded to the appropriate sizes, it makes
excellent quality sands for all purposes and is widely used. I get
what he calls 3 mm (actually about 1 - 5 mm) from a local sand and
aggregate merchant, approx GBP25 delivered for a 'dumpy bag', about a
ton I guess.

Feldspar minerals do convert to clays, but only over a great many
millions of years!


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net