Monday, March 15, 2010

Collection Management - II

Each item in a collection needs:
  • a unique descriptor (e.g., specimen number),
  • an accompanying label,
  • a permanent record,
  • and safe, accessible storage.
In this post, I will discuss the unique descriptor.

Typically, this is a unique number assigned to the specimen. It may also be an alphanumeric character string, a bar code, etc.; but a symbol that requires a sophisticated scanner to read assumes that scanning system will be available for the useful life of the specimen (which may be centuries).

For minerals, this number is usually affixed to the specimens, either by writing or painting it on the specimen, or by attaching a printed label with permanent glue.

For loose gemstones, typically each gemstone has its own box, and a label with the descriptor is affixed to the box. As the label is not physically attached to the stone, it helps to include the gemstone weight on its label as a quick (but not exact) check for its identity.

Every record for this specimen should include the descriptor. Descriptor should not be used for more than one specimen (except in the case of bulk samples, where each bulk sample needs a unique descriptor, and individual grains in the sample only need separate descriptors when they are separated out for some purpose, like research or display). Descriptors should never be reused, since even if a specimen is destroyed, lost, or traded away, its records should remain with the collection.

I provide collection management services professionally, so feel free to contact me!

Thursday, March 11, 2010

What is Collection Management?

Whether you have a small mineral collection that has outgrown its single bookshelf, or a few more gemstones than fit into one box, or a large personal collection, or even a museum-grade collection of 1000 pieces or more, you probably need collection management. Let's explore what's involved in this service (which I can provide, of course).

Collection management occurs on several levels. Its main goal is to keep each specimen associated with the information that gives it value or importance. Thus, it creates and maintains linkages between the specimen and its history.

Wednesday, March 3, 2010

Minerals, Gems, and Crystals

Recently I've been giving a talk on the difference between mineralogy and gemology. (Mineralogy studies minerals, gemology studies gems; but there are other differences and similarities.)

When I explain things more than once, I keep trying to make the explanation simpler and clearer.

A mineral is defined by its (essential element) chemistry and crystal structure. There are many sites that explain this.

A gem is defined by its properties. If the gem is also a mineral, these properties are based on its essential element chemistry and crystal structure, but can also be due to:
  • Trace elements (Cr and V in emeralds, Cr in rubies)
  • Inclusions (cat's-eyes and star stones)
  • Texture (the interlocking texture in jadeite, the felted texture in nephrite)
  • Grain size and lack of inclusions, leading to diaphaneity: transparent to translucent to opaque; the greater the transparency, the greater the likelihood a sample is gem-quality.
(And some gems are not minerals: pearls, opal, jet, ivories, amber, etc.)

As a related topic, I see the term crystal used to mean different things to different people in the gem and mineral business.
  • Mineralogically, a single crystal is a connected structure retaining orientation from one end to the other. (In a mosaic crystal, sub-blocks of the structure have slightly different orientations, which can lead to large changes on orientation from one end to the other, like in saddle-shaped dolomite crystals.)
  • To an emerald dealer, "crystal" means a fine quality emerald that will hold up well to cutting.
  • To a mineral collector, a crystal should retain all its natural surfaces; but to someone in the metaphysical community, polished surfaces may be acceptable.
  • By people who deal in glass imitations, I have seen "crystal" used as it is used for glassware: a high-refractive index material (often containing lead) that would still be considered amorphous to mineralogists.
  • A crystal ball should be quartz, not glass; sometimes "crystal" is short-hand for rock crystal quartz, the colorless transparent variety.

Monday, March 1, 2010


Old friend and fellow mineralogist Vandall King recommended that I start a blog, so here it is. In future installments, I hope to tell stories about minerals and gems, so stay tuned!

But first, some words from my sponsor. My company, Mary Johnson Consulting, has a website with my background. The site,, is active but updated infrequently. (The site includes some of my zoo sketches as well.)

I also have an exciting service for anyone who needs ideas about minerals, gems, their durability, curation, display, etc.: one half-hour discussion for new clients for $25. For half of the time we discuss your problem and for the remaining 15 minutes we brainstorm on possible solutions. Contact me at with BRAINSTORM as the subject line if you are interested.

Finally, my book Gemstones: A Complete Color Reference for Precious and Semiprecious Stones of the World, by Karen Hurrell and yours truly, is available from Barnes & Noble ( Reviews have been quite positive, and the first edition, out now, has an enjoyable typo on page 184.
ISBN: 1435106105 or ISBN-13: 9781435106109.