Gem of the Month
Each month this section will feature either a topic of
interest to gem lovers or one special gemstone with background on the
material and its value.
Go to: Homepage
-- what's new at ACS --
monthly specials and
discounts -- "buried
treasures" -- BWS/FS jewelry
designs -- gem topic of the
month -- gem topic
archive -- birthstones
-- ask Barbara --
key to all the codes used on the ACS
site -- definitions of
terms used on the ACS site
-- how to order
-- about ACS --
setting these gems
-- free gemology course
-- Mail to
barbara@acstones.com
Dendritic, Moss and Plume
Agates
A subvariety of chalcedony or microcrystalline
quartz, these agates have in common that they contain mineral
inclusions which may be any color, but share a roughly tree-like or
branching form (dendron = tree). Those which have a more plant or
feather-like appearance have been called moss or sagenitic or plume
agates, respectively. All agates take a wonderful polish and are
tough enough for most jewelry uses. Designers often take advantage of
the intriguing patterns these stones have to offer.



[Dendritic
Agates]
In general agate prices are quite modest with
most of the price paying for the fashioning rather than the material
itself. In the case of these agates, those with particularly
distinctive or landscape like patterns or those of especially large
size are at a premium. Custom cutting or pieces from collectible
locations would be substantially more expensive. Pieces with
especially fine patterns can be quite valuable.

[Moss
Agates]



[Plume or Sagenitic
Agates]
Gemological Data:
Makeup: Silicon dioxide, in
cryptocrystalline form
Luster: vitreous
Hardness: 7
Crystal structure: trigonal
Cleavage: none
Fracture: conchoidal
Density: 2.60 (+.10, -.05)
RI: 1.53-1.54
Birefringence: none to .004
Pleochroism: none
Dispersion: none
Stones Currently Available:
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our Catalog}
Go to: Homepage
-- what's new at ACS --
monthly specials and
discounts -- "buried
treasures" -- BWS/FS jewelry
designs -- gem topic of the
month -- gem topic
archive -- birthstones
-- ask Barbara --
key to all the codes used on the ACS
site -- definitions of
terms used on the ACS site
-- how to order
-- about ACS --
setting these gems
-- free gemology course
-- Mail to
barbara@acstones.com