-
Non-Destructive Tests
A) Tarnish: Most specimens of pyrite, found in nature, will have at least some tarnish on their surface. Nuggets or small flakes of gold are usually bright and untarnished. B) Color: Pyrite has a brassy color. Gold has a golden to yellow color. Most native gold is alloyed with silver, and if the silver content is high enough, the specimen…
-
Separating Fool’s Gold from Gold
Here are a few simple tests that almost anyone can use to tell the difference between pyrite and gold. They can usually be done successfully by inexperienced people. However, wise people obtain a couple small pieces of pyrite and a couple small pieces of gold and use them to gain valuable experience. CAUTION: All pieces…
-
What Is Fool’s Gold?
“Fool’s gold” is a common nickname for pyrite. Pyrite received that nickname because it is worth virtually nothing, but has an appearance that “fools” people into believing that it is gold. With a little practice, there are many easy tests that anyone can use to quickly tell the difference between pyrite and gold. The nickname “fool’s gold”…
-
Imitation Rhodochrosite
Beads and cabochons made of imitation rhodochrosite are in the gem and jewelry market. They are made from powdered mineral matter, in pink and white colors, and bound together with resin. The powders are layered and swirled together to produce a banded appearance similar to much natural rhodochrosite. To the unaided eye, the material looks…
-
Rhodochrosite as a Gemstone
Rhodochrosite is a favorite gemstone of many people. It is often slabbed to show off its banded or concentric patterns. Most of the slabs are used to cut cabochons. Cutting rhodochrosite is a difficult job because the material has perfect cleavage, and it is so soft that it can be difficult to polish. Nice, stable, slabbed material is…
-
Geologic Occurrence
The formation of rhodochrosite usually occurs in fractures and cavities of metamorphic and sedimentary rocks. It is often associated with silver deposits, and a few silver mines produce rhodochrosite as a byproduct. Some of the common modes of occurrence and their lapidary uses are described below. In metamorphic rocks, rhodochrosite is found as a vein and fracture-filling mineral where it precipitates from…
-
Physical and Chemical Properties
Rhodochrosite has a variable chemical composition. It is a manganese carbonate, but the manganese is frequently replaced by iron, magnesium and/or calcium as shown in this formula: (Mn,Fe,Mg,Ca)CO3. These substitutions of other elements for manganese change the composition and alter the specific gravity, hardness, and color of the mineral. The bright pink color can become grayish,…
-
What is Rhodochrosite?
Rhodochrosite is a manganese carbonate mineral that ranges in color from light pink to bright red. It is found in a small number of locations worldwide where other manganese minerals are usually present. Rhodochrosite is sometimes used as an ore of manganese but is rarely found in economic quantities. Specimens with a wonderful pink color are used to produce highly…
-
Grape, Yes. Agate, Maybe Not.
The name “grape agate” has stuck as a marketing term. However, the name is a misnomer. Misnomers are names that are scientifically incorrect. There are no arguments with “grape” because of its purple color. But, the use of “agate” as a species/variety name draws objections. Here is an analysis… Grape Agate: This name is inappropriate because agate should…
-
What Is Grape Agate?
Grape agate is a marketing name for purple aggregates of tiny quartz crystals with a spherical (botryoidal) habit. The name reflects their purple color and how they occur in clusters that resemble bunches of grapes. This material is found in the Mamuju area, near the western coast of Sulawesi, an island of Indonesia. Grape agate entered the mineral market…