earth science

Robertsite

Robertsite is a earth 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 Robertsite rather than just read about it. In short: Robertsite, Ca3(Mn3+)4[(OH)3| (PO4)2]2·3(H2O) (alternatively formulated Ca2(Mn3(PO4)3O2)(H2O)3), is a secondary phosphate mineral named for Willard Lincoln Roberts (1923–1987), mineralogist and professor at South Dakota School of Mines in Rapid City, South Dakota. The type locality for Robertsite is the Tip Top mine, Custer County, South Dakota, US.

Key takeaways

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

Reference excerpt

Robertsite, Ca3(Mn3+)4[(OH)3| (PO4)2]2·3(H2O) (alternatively formulated Ca2(Mn3(PO4)3O2)(H2O)3), is a secondary phosphate mineral named for Willard Lincoln Roberts (1923–1987), mineralogist and professor at South Dakota School of Mines in Rapid City, South Dakota. The type locality for Robertsite is the Tip Top mine, Custer County, South Dakota, US. Robertsite occurs at the Tip Top Mine as minute crystal aggregates and crusts found on quartz associated with triphylite. It is a dark reddish brown to black monoclinic mineral. It occurs as a secondary mineral in pegmatite. It is also reported from the Khoa Rang Kai phosphate deposit, Chiang Mai, Thailand in a limestone guano deposit. It is associated with rockbridgeite, ferrisicklerite, leucophosphite, jahnsite, montgomeryite, collinsite and hureaulite in the type locality. In the guano deposit it occurs with carbonate-fluorapatite, calcite, dolomite, quartz and clay minerals. In the Omo Valley of Ethiopia it occurs with mitridatite associated with fossil fish in Pliocene/Pleistocene lake sediments. Recently, in an exploration conducted by the Italian La Venta Geographical Association, confirmed the existence of Robertsite in the Puerto Princesa Subterranean River National Park, located about 50 kilometres (31 mi) north of the city center of Puerto Princesa, Palawan, Philippines.

Mitridatite group: Arseniosiderite-mitridatite series: Ca2(Fe3+)3[(O)2|(AsO4)3]·3H2O to Ca2(Fe3+)3[(O)2|(PO4)3]·3H2O Arseniosiderite-robertsite series: Ca2(Fe3+)3[(O)2|(AsO4)3]·3H2O to Ca3(Mn3+)4[(OH)3|(PO4)2]2·3H2O

References

Frank C. Hawthorne (1998). "Structure and chemistry of phosphate minerals" (abstract page). Mineralogical Magazine. 62 (2): 141–164. Bibcode:1998MinM...62..141H. doi:10.1180/002646198547512. S2CID 38295867. Moore, P.B. (1974). "Isotypy of robertsite, mitridatite and arseniosiderite". Am. Mineral. B59: 55–59. Andrade, M. B., Morrison, S. M., Di Domizio, A. J., Feinglos, M. N., & Downs, R. T. (2012). Robertsite, Ca2MnIII3O2 (PO4) 3.3 H2O. Acta Crystallographica Section E: Structure Reports Online, 68(10), i74-i75.doi:10.1107/S160053681203735X

Illustrations

Worked examples

Example 1 — a first encounter with Robertsite

Start with the simplest possible case. Write down what Robertsite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth 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 Robertsite 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 Robertsite 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 Robertsite

In research: Robertsite appears in earth 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 Robertsite 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: Robertsite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Manganese(III) minerals, Minerals in space group 15, Monoclinic minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Robertsite 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 Robertsite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Robertsite 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 Robertsite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Robertsite in simple terms?

Why does Robertsite matter?

Because it connects several earth 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 Robertsite?

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 Robertsite.