"Oren" wrote in message
news
On Tue, 26 Mar 2013 19:39:43 -0700 (PDT),
wrote:

Was that based on stock white shingles or shingles painted white?
Because surfaces painted white reflect roughly 90% of the sunlight,
while regular white shingles reflect only 10%.


Years ago, a flat roof in Florida had a white quartz on them. In the
desert here, I have seen a couple that used white rocks. Strange,
considering the weight of the rock of the roof and the home age.

Sample photo:

http://www.navarroroofing.com/images/rock-roof-redondo-beach.jpg



A quartz rock is really not that heavy, about 150 # per cubic foot
So small 1/8"- 1/4 quartz crystal, an inch think would weigh about 12# per
square foot.
Not that heavy at all.