Rocks as Gems

The word “rock” doesn’t normally conjure up images of beautiful jewelry, but as I explained in my very first blog post (https://mochisgifts.com/2014/06/05/gem-vs-mineral/), some rocks are also considered gems. While many minerals meet the criteria of beauty, rarity, and durability to be considered gems, very few rocks do.

Because the conditions under which rocks form can vary greatly, there can be very different looking results. Even within a specific type of rock, although the main mineral components are the same, trace elements or other minerals, sizes of individual grains, relative amounts of each mineral, and more, may differ. Causes for these differences include: the elements available in the melt source, temperature, and pressure. Most of the rocks used as gems have individual minerals that are visible to the naked eye, but some, such as basalt (sold as “lava”) have mineral grains too small to see. This variability is part of the beauty of the rock, but can also make it very difficult to match pieces for jewelry.

Enjoy these examples of rocks that are gems – I’ve listed the main constituent minerals.

Lapis lazuli

Blue: lazurite
Brassy/gold: pyrite
White: calcite

Ruby in zoisite

Green: zoisite
Red: ruby
Black: hornblende

See my blog: https://mochisgifts.com/2019/07/03/ruby-in-zoisite/

Tiger Iron

Gray: hematite
Gold: tigers eye
Red: jasper

See my blog on hematite: https://mochisgifts.com/2014/10/17/hematite-synthetic-hematite-and-disclosure/

Unakite

Green: epidote
Pink/orange: potassium feldspar
Gray: quartz

Lava (basalt)

Individual grains too small to see but include:
Plagioclase feldspar
Pyroxene minerals
Olivene
and many other accessory minerals

Graphic Granite

(labeled as “feldspar” when I purchased it)
Gray: quartz
White: feldspar
and many other accessory minerals

So yes, we geologists love rocks, but now even non-geologists have a reason to enjoy them too!

How Much is my Jewelry Worth?

How much is my jewelry worth?  I’m asked this at every show.  As a gemologist I can identify the gemstones in your jewelry, but to answer the question of value, the right person to ask is an appraiser.  I’ve asked my colleague, Jeanne Hawk, a GIA Graduate Gemologist, Registered MasterValuer and Certified Insurance Appraiser, to be a guest blogger this month:

Establishing and substantiating the value of an item are what appraising is all about. An appraisal is an opinion of value, a well-researched conclusion that is supported by facts which are interpreted from the marketplace. Most jewelry appraisals are done for obtaining insurance coverage. An insurance appraisal is used to determine the retail replacement value of a jewelry item. Other appraisal types include those done to determine fair market value for estate items and items sold for scrap value.

Many of my clients have jewelry of unknown identification or value. I do consultations to identify the gemstones and/or diamonds and metal karatage to determine what you have and whether you should keep it, insure, or scrap it, as is often the case with outdated gold chains. I’ll let you know the market value if you plan to sell it. And if it’s something you want to insure, I can prepare an appraisal for you.

There are six steps involved in the appraisal process as follows: 1) establish the scope of the appraisal, 2) plan the appraisal, 3) collect and analyze the data, 4) apply a valuation approach, 5) set limitations and contingency conditions, and 6) supply the final estimate of value.

At the present time anyone can call oneself a professional jewelry appraiser. However, self-anointing does not confer expertise. The key is education. A gemologist who has undergone formal gemological training, holds a degree or special education in valuation science, and has buying and selling experience either on a wholesale or retail level has the basic prerequisites of an appraiser. The valuation must be done by an individual with suitable qualifications who has no interest (no bias) in the item. Participation in professional appraising organizations is important, as well. It is critical that any jewelry appraisal be developed and written in accordance with the Uniform Standards of Professional Appraisal Practice (USPAP), authorized by Congress as the source of appraisal standards and appraiser qualifications.

I am a certified Gemoljeanne_cropogical Institute of America (GIA) Graduate Gemologist (GG), qualified to accurately identify and grade the gemstones in your jewelry. As a Registered Master Valuer™ and Certified Insurance Appraiser™, I am trained in appraisal valuation techniques and can appropriately value and appraise your jewelry. All appraisal reports are prepared in accordance with USPAP.

At your appraisal appointment, I will clean, identify, measure, weigh, grade, and photograph your jewelry. Most appointments take 30 minutes; longer appointments may be needed for multiple items. You will leave with your jewelry. In 7-10 business days, once I have completed the valuation part of the appraisal, you will receive your appraisal via email. Payment for the appraisal, and any hard copies requested, is due at the time of your appointment. Would you like to learn more about how the value of jewelry is determined? Find out in my FREE report! Call this 24 hour toll free recorded message to request your report. 1-800-579-3932.

Jeanne Hawk Fine Jewelry Appraisals specializes in gem identification, diamond grading, jewelry appraisals, market value estimations, general consultation, and quality assessments. To best meet my clients’ needs, services are provided by appointment only. I can be reached at 831-359-3449 or via email at info@hawkjewelryappraisals.com to schedule an appointment. The office is located at 5521 Scotts Valley Drive, Suite 235, Scotts Valley, CA 95066. The company website is http://www.hawkjewelryappraisals.com. Give me a call or visit my website today!

 

Turritella Agate – A Snail By Any Other Name …

FTGFN105_a

Fossil turritella agate & garnet necklace (Item FTGFN105)

In last month’s blog I explained that for many gemstone beads, the country of origin may be difficult to determine.  Fossil turritella agate is an exception because it comes exclusively from the Green River Formation in Wyoming, USA.

Turritellas are marine snails (gastropods) with spiral shells.  When fossil snails were found in the Green River Formation, they looked like turritellas and were given that name.  However, it turned out that the snails were in fact an extinct freshwater variety and were renamed Elimia tenera.  By that time, the incorrect name had already become commonly used and the name elimia tenera has never managed to replace the incorrect turritella name.

Turritella fossils are among my favorite fossils to incorporate into my jewelry designs; the fossil snails are creamy to white spirals in a rich brown to almost black matrix.  The polish can be uneven on these stones due to the natural variation in the fossils, but that’s part of what makes each one unique.

The following is directly from http://geology.com/gemstones/turritella/:

“How did Turritella Agate Form?

About 50 million years ago, during the Eocene epoch, the young Rocky Mountains were almost finished growing, and the landscape of what is now parts of Colorado, Utah, and Wyoming consisted of rugged mountains separated by broad intermountain basins. Rains falling on the slopes of these mountains ran off of the land and collected into streams that carried sand, silt, mud, and dissolved materials down into the lakes that occupied the intermountain basins. Over time, these sediments began filling the lakes, and many types of fossils were preserved within them.

Abundant plants and algae grew on the margins of these lakes, providing a perfect habitat and food source for Elimia tenera, the freshwater snail. When the snails died, their shells sank to the bottom of the lake. The snails were so prolific that entire lenses of sediment were composed almost entirely of their shells.

After these layers were buried, groundwater moved through the sediments. Small amounts of microcrystalline silica that were dissolved in the groundwater began to precipitate, possibly in the form of a gel, within the cavities of the snail shells and the empty spaces between them. Over time, the entire mass of fossils was silicified, forming the brown fossiliferous agate (also known as chalcedony) that we know today as Turritella agate.”

References:

FTGVE102_Nov15_a

Fossil turritella agate & garnet earrings (Item FTG2)

http://geology.com/gemstones/turritella/
https://en.wikipedia.org/wiki/Elimia_tenera