Boulder Opal Nomenclature
All industries have their own terminology to describe specifics about the industry.
Below is a list of words/phrases that are opal industry centric with a special focus on Boulder Opal.
Blocking Out - cutting term: means to expose the profile of the opal vein so the cutter can decide how to go about facing down.
Boulder Black – grading term. Applies to top quality color.
Boulder Splits – when the host rock shears apart along the vein of opal exposing 2 opal faces.
Cut stone – grading/selling term. Gemstones for setting into jewelry or investment.
Deposit – mining term. A deposit is a cluster of opal usually found in faults in the earth’s strata.
Dumps – mining term. Dumps are piles of rocks put to one side to be sorted later.
Face – generic term. In mining an opal face is a rough face. A large show of opal within the natural setting. As a cutting term a face means the show of opal color that is evident when the gemstone has been cut.
Facing down – cutting term. To remove the boulder rock or common opal from one side of the opal vein to expose the color.
Gem grade – grading term. Opal with complexity of color.
Gouger - mining term, means a prospector who “scratches” for opal.
Matrix – type of opal. Ironstone / sandstone composite with opal impregnated within.
Parcel of rough – mining/selling term. A group of opal bearing rocks.
Pick up – mining term. Means to walk behind the dozer and pick up any opal found on the ground after the teeth of the machine have loosened the opal bearing dirt.
Pipe opal – type of opal. Pipe opal is opal that has piped it way through sandstone/ ironstone.
Polytop finish – cutting term. A polytope is a polymer seal on the face of an opal stone making it more robust.
Potch – another name for common opal.
Potchy blue – potch (common opal) that is predominately blue in color.
Presence of piece – grading term. A way of describing the natural aura of the opal gemstone.
Raw opal – another term for rough opal.
Rough opal – opal found in nature.
Sandy boulder – where the host stone is mostly sandstone, generally a softer ore.
Spec – abbreviation for specimen.
Spec grade – specimen grade
Stone – abbreviation for gemstone
Traditional finish – an opal is highly polished by a process of removing scratches, using sanders and polishers.