In article , Pete wrote:
` Chalcedony is a variety of cryptocrystalline quartz with extremely small
` crystals and a specific gravity (weight under water, a measure of a
` rock/mineral's purity) nearly identical to that of pure quartz. Due to its
` very high quartz content and super fine particle matrix, chalcedony has a
` very waxy luster.

Yipes, what a horrendously mangled misdefinition of specific gravity.
By that definition, water has a specific gravity of 0, and wood has
a negative sg. I guess it's a mistranslation of something from another
language,

Yuck.
Looking elsewhere ...
This large group includes all minerals with the primary chemical formula 5i02
(silicon dioxide) and is most abundantly represented in nature by pure quartz
and its many cryptocrystalline forms.

Now that looks like OCR gone wrong.

I don't recognise the names of the "maintainers" of the page, but looking around,
I think it's something maintained by the *geography* department. Can't expect them to
get rocks right. Or to walk straight while chewing gum.

I'll mention it next time I'm in the department. Or maybe I won't - I might be
asked to do the maintenance.

--
Aidan Karley FGS
Aberdeen, Scotland,
Location: 57°10'11" N, 02°08'43" W (sub-tropical Aberdeen), 0.021233