fossil preparation

where is your fish from?

• Ulrich Quarries in Wyoming

• Fossil syncline lake

• Eocene ~50 mya

• Fine grain, calcareous shale of the Green River Formation

knightia

most common, herring-like, likely schooled & fed on seed shrimp, algal forms, & diatoms

diplomystus

largest herring genus, likely fed on other two types of fish

priscacara

unlikely

free from matrix

in gravel beds of streams/washed up on beach

mostly free

crown/enamel of tooth in soft matrix

still in matrix

may be supported w/ a plaster jacket for transport after being dug out

methods of preparing fossils in matrix

1. physical

   • hand tools

   • mechanical/powered tools - pneumatic (air pens/air abrasives) OR electric powered (dremels/engravers)

2. chemical

   • consolidants & adhesives

   • acids & more

hand tools

• Sharp probes

• Dental picks

• Chisels

• Hammers

• Awls

• Pin vises

• Brushes

  • Tungsten carbide tips

mini air hammers

uses reciprocal motion of a hard, sharp point/pen at tens of thousands of cycles per min

• air scribes or air engraving pen

air abrasive devices

uses a small stream of air propelled grit/particles

• good for cleaning micro-fossils & finishing

etchers/engravers

reciprocating stylus; better for more delicate specimens due to exerting less force

electric rotary grinders

hand-held grinders; can be used primarily for finishing up

• burrs, cutting wheels, & grinding bits

consolidants (hardeners)

• “resins which have been dissolved in a solvent.”

• help prevent deterioration of specimens

types of consolidants

• pure resins

• emulsions

recommended pure resins

butvar & acryloid/paraloid B-72

• specimen needs to be completely dry

• hard, durable, reversible, cheap

• acetone as solvent

emulsions

NOT recommended:

• difficult to reverse, especially after UV exposure → tend to yellow

• may be used for soft, wet bone

adhesives

• glues used to repair specimens

• reversibility is ideal

types of adhesives

animal glues, epoxy resins, Elmers, super glues, & cellulose nitrates

• butvars & acrylic polymers recommended

acids & more for dissolving rock

used in dilute amounts to dissolve matrix surrounding fossils

• type of rock & concentration vital

• surfactants (like in detergents) can be used for calcitic fossils

dangers of acids

chemicals may be hazardous to human, may damage the fossil, can take a very long time

benefits of acids

may be needed for delicate fossils that could be damaged by vibrations/forces from physical tools