science

Sunstone

Sunstone is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sunstone rather than just read about it. In short: Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance. It has been found in Southern Norway, Sweden, various localities in the United States, and on some beaches along the midcoast of South Australia.

Key takeaways

Sunstone belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sunstone to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sunstone from memory before moving on to harder problems.

Reference excerpt

Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance. It has been found in Southern Norway, Sweden, various localities in the United States, and on some beaches along the midcoast of South Australia.

Properties

Physical properties

The optical effect is due to reflections from inclusions of red copper, hematite, or goethite, in the form of minute scales, which are hexagonal, rhombic, or irregular in shape, and are disposed parallel to the principal cleavage-plane. These inclusions give the stone an appearance something like that of aventurine, hence sunstone is known also as "aventurine-feldspar". The optical effect is called schiller and the color of Oregon Sunstone is due to copper. The middle part of this crystal sparkles, and usually the color is darkest in the middle and becomes lighter toward the outer edges. The feldspar which usually displays the aventurine appearance is oligoclase, though the effect is sometimes seen in orthoclase: Hence two kinds of sunstone are distinguished as "oligoclase sunstone" and "orthoclase sunstone".

Distribution Sunstone was not popular until recently. Previously the best-known locality being Tvedestrand Municipality in Agder county in southern Norway, where masses of the sunstone occur embedded in a vein of quartz running through gneiss. Other locations include near Lake Baikal in Siberia, and several United States localities – notably at Middletown Township, Delaware County, Pennsylvania; Plush, Oregon; and Statesville, North Carolina. The "orthoclase sunstone" variant has been found near Crown Point and at several other localities in New York, as also at Glen Riddle in Delaware County, Pennsylvania, and at Amelia Courthouse, Amelia County, Virginia. Sunstone is also found in Pleistocene basalt flows at Sunstone Knoll in Millard County, Utah.

Oregon sunstone

A variety known as "Oregon sunstone" is found in Harney County, Oregon and in eastern Lake County north of Plush. Oregon Sunstone contains elemental copper. Oregon Sunstone is unique in that crystals can be quite large. The copper leads to variant color within some stones, where turning one stone will result in manifold hues: The more copper within the stone, the darker the complexion. On 4 August 1987, the Oregon State Legislature designated Oregon Sunstone as its state gemstone by joint resolution.

Andesine controversy In the early 2000s, a new variety of red or green gemstone resembling sunstone and called "andesine" appeared in the gem market. After much controversy and debate, most of these gemstones, allegedly sourced from China, were subsequently discovered to have been artificially colored by a copper diffusion process. A Tibetan source of bona fide (untreated) red andesine, however, was eventually verified by a number of independent groups of well-respected gemologists.

See also Andesine Feldspar Rainbow lattice sunstone

References

This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Sunstone". Encyclopædia Britannica. Vol. 26 (11th ed.). Cambridge University Press. p. 110.

External links

"Mineralogy database" (main) – via webmineral.com. Saab, Patricia. "Oregon Sunstone". The Oregon Encyclopedia.

Illustrations

Sunstone: Unpolished sunstone — Unpolished sunstone

Worked examples

Example 1 — a first encounter with Sunstone

Start with the simplest possible case. Write down what Sunstone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sunstone before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sunstone ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sunstone

In research: Sunstone appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sunstone in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sunstone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alkali feldspar series, Aluminosilicates, Gemstones, so understanding it makes those chapters shorter.
In everyday life: Look for Sunstone outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sunstone in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sunstone means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sunstone out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sunstone in simple terms?

Why does Sunstone matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sunstone?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sunstone.