Gem Localities Of the 1990s

Abstract

The past decade saw growth in gem exploration, production, and marketing worldwide. Important colored stone-producing regions

The presence of trapped carbon dioxide in lapis lazuli and its potential use in geo-sourcing natural ultramarine pigment

“…Geologists and archaeologists are skeptical of whether an ancient or even modern Iranian source actually exists, and many lapis lazuli samples labeled as 'Iranian' are thought to have originated elsewhere [3,4,6]. No Iranian source was identified in a 1990 list of commercial lapis lazuli sources [33] nor has one been identified by geological surveys [4]. It is presumed that ancient texts alluding to a Persian (Iranian) source of lapis lazuli where either confused with rocks traded through that area, but not originating there, or with other blue mineral resources such as lazulite or turquoise [4].…”

Non-pegmatitic Deposits of Beryllium: Mineralogy, Geology, Phase Equilibria and Origin

“…Beryllium minerals in the BASH group typically resist weathering and thus they occur in placer deposits. Alluvial deposits, particularly in Sri Lanka and related Gondwanan occurrences, are major sources of gem aquamarine, chrysoberyl and taaffeite-group minerals (Menon and Santosh 1995;Dissanayake et al 2000;Shigley et al 2000). These materials can be of unusually high quality because alluvial processes preferentially remove damaged (flawed) parts of crystals (Sinkankas 1981).…”

Gemstone Enhancement and Detection in the 1990s

“…The disclosure that such substances were present in fractures and surface depressions caused a great deal of controversy in the industry, which contributed to the significant drop in price of heat-treated rubies in the latter half of the decade (see, e.g., Peretti et al, 1995;Shigley et al, 2000a). Many in the industry felt that this material was only a by-product of the heating process (Robinson, 1995), while others felt that it was put there intentionally (Emmett, 1999).…”

“…As a result of several events during the decade, consumers became aware that emeralds are routinely fracture filled, a fact that retailers typically were not disclosing. This new awareness coupled with the general lack of disclosure caused the public to feel that there must be something wrong with emeralds and they stopped buying them, creating a precipitous drop in the sale and value of these stones (see, e.g., Shigley et al, 2000a). This is just one example of events throughout the '90s that made the subject of treatments-what they involve, how they can be identified, and how they should be disclosed-the most discussed gemological issue of the decade.…”