First of all : To this very minute I am not very happy about the title of this project. "Giant crystals" sounds a tad too bombastic for me and in fact is a rather unscientific term, though it was earlier used in scientific publications. But I simply dont know a better name. "Large crystal" sound a bit too flat. "Extraordinary large crystals" is somewhat unprecise and too long. "Megacryst(al)s" may be the proper scientific name, but fails to meet public interest. So for the time being I think I stick to "giant crystals"...
But what is a giant crystal ?
This is a question which seems on first view easily to answer,
but in fact it is very difficult, if not impossible to find an appropiate
answer. But we will try !
A 10 cm quartz crystal would be considered
by most people as normal sized. But how about a 25 cm quartz crystal ? Is a 25
cm large quartz crystal a giant crystal ? Some mineral dealers will claim so, but considering
the abundance of 50, 60 or 70 cm large quartz crystals in the European
Alps and elsewhere, 25 cm appears not exceptional large. But
how about other minerals ? If we define a 25 cm large quartz crystal as
quite normal, what about a 25 cm fluorite crystal or maybe
a 25 cm long erythrite ?. Both would be very large, if not giant crystals
for this particular species. So where to draw the line...?
Another thought : A 1 m thin helicite of calcite
- commonly called calcite straw - or spaghetti - may weigh only some kg or even less, though it is a valid 1 m long monocrystal
of calcite. A one meter cube of halite weighs about 2 tons. So
a large crystal of a cubic mineral like halite, fluorite
or pyrite may contain significant more mineral substance than an slender
calcite crystal. Again : Where to draw
the line ?
1 m long soda straw calcite crystals compared
with a 1 m sized blocky
orthoclase crystal in the Ingersoll mine / Black Hills,
Consequently we have difficulties to precisely
define a giant crystal. Here we will - regardless
of possible exceptions - generally use a 1 m ( = 3 feet) limit for a giant crystal, i.e. a crystal must reach or exceed 1 m = 3 feet size in at least one dimension to qualify as giant crystal.
There will be some exceptions from this rule, as some really remarkable specimens of relatively rare minerals like erythrite simply dont reach the 1 m size. However a 50 cm crystal of erythrite - said to have been found at Bou Azzer in Morocco, but not confirmed yet, certainly is giant enough to get an entry on this site, if we can verify its occurence.
Another exception are giant crystal aggregates. If they are larger than 1 m they will be included, regardless of the individual size of the crystals. Ok... we will NOT include a marble mass or the dolomites of the southern Alps etc, but i think you got the idea.
A third exemption will be native elements, which sometimes form giant crystalline (monocrystalline ?) aggregates like the native copper masses of the Keeweenaw peninsula or the famous "Silver Sidewalk" at Cobalt, Ontario.
A fourth exeption will be...but hold on, we might need a spare one later! So far for the theory. And now enjoy this site !