SSC CGL 2024 Tier-I · 18 September 2024, Shift 3 · General Awareness · Question 25 of 98

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Which of the following is an inosilicate amphibole mineral used in highway construction and as railroad ballast?

(a)Hornblende
(b)Olivine
(c)Shale
(d)Geyserite

Answer

Why

Correct — A. Hornblende is an amphibole, and amphiboles are inosilicates — silicates whose SiO4 tetrahedra are linked into chains, double chains in the amphibole case.

It is a common dark mineral in granite, diorite and amphibolite, and rock rich in it is hard enough to be crushed for road metal and railway ballast, which is the use the stem names. Option (a) is the amphibole in this list.

Why the others are wrong

(b)
Olivine — Olivine is a nesosilicate: its tetrahedra stand alone instead of linking into chains. It is a silicate and common in basalt, but it is not an amphibole.
(c)
Shale — Shale is not a mineral at all. It is a fine-grained sedimentary rock of clay and silt, and it splits too easily to serve as ballast.
(d)
Geyserite — Geyserite is a siliceous sinter deposited around geysers and hot springs, a form of opaline silica. It is neither an amphibole nor a construction stone.

Concept

Silicates are classified by how their SiO4 tetrahedra connect, and those class names are what questions like this one are really testing.

Isolated tetrahedra give nesosilicates, such as olivine. Single and double chains give inosilicates, which cover the pyroxenes and the amphiboles. Sheets give phyllosilicates such as mica, and a full three-dimensional framework gives tectosilicates such as quartz and feldspar.

Hornblende is the everyday amphibole: dark green to black, common in igneous and metamorphic rocks, and quarried along with its host rock for aggregate.

The stem classifies the mineral for you — 'inosilicate amphibole' fixes the class, so the item reduces to naming the mineral that belongs to it.

Key facts

Hornblende is an amphibole, and amphiboles are double-chain inosilicates.
Olivine is a nesosilicate built from isolated silicate tetrahedra.
Shale is a sedimentary rock rather than a mineral.
Geyserite is siliceous sinter deposited around geysers and hot springs.

Study next

Silicate classification from nesosilicates to tectosilicatesRock-forming minerals of igneous rocks: quartz, feldspar, mica, pyroxene and amphiboleThe three rock families and how each is formed

Common traps

Picking shale because it sounds like a building material.
Assuming any dark, hard mineral qualifies as an amphibole.
Confusing pyroxenes with amphiboles — both are inosilicates but the chains differ.

SSC keeps physical geography at the level of one-line definitions — exfoliation as a form of physical weathering is asked on 13 Sep 2024, 12:30, GA Q.12.

Related PYQs

No directly related past PYQ was found.