How do you use the Scheme for Igneous Rock Identification on the Earth Science Reference Tables?

Read the chart in two directions. Top to bottom gives texture (crystal/grain size), which is set by cooling rate: coarse (large crystals) means slow cooling deep underground (intrusive), fine (small crystals) means fast cooling at the surface (extrusive), and glassy means very rapid cooling. Left to right gives composition, color and density: felsic rocks (granite, rhyolite) are light and low density, mafic rocks (gabbro, basalt) are dark and dense. To name a rock, match its texture and its composition: a coarse, light rock is granite; a fine, dark rock is basalt.

What is the most reliable property for identifying a mineral on the Regents?

Streak, hardness and cleavage are far more reliable than color, because color changes with small impurities. Streak is the color of the mineral's powder on an unglazed plate and is consistent for a given mineral. Hardness (the Mohs scale, tested with a fingernail at about 2.5, a penny at about 3.5, and glass or a steel file at about 5.5) and cleavage (breaking along flat planes) reflect the mineral's structure. Use the Properties of Common Minerals chart, starting with luster (metallic or nonmetallic), then hardness and cleavage, then a distinguishing test such as the acid fizz for calcite.

How do you find the distance to an earthquake epicenter with the Reference Tables?

Use the S-minus-P time. On a seismogram, measure how long after the P-wave the S-wave arrives. On the Earthquake P-wave and S-wave Travel Time graph, find the place where the vertical gap between the S-wave and P-wave curves equals that time difference (mark the gap on the edge of a paper strip and slide it between the curves), then read straight down to the distance axis. The larger the S-minus-P time, the farther the station from the epicenter. Three stations are needed to fix the epicenter, because each station gives only a circle of possible locations.

How do you calculate the rate of sea-floor spreading?

Use the rate-of-change equation from page 1 of the Reference Tables: rate equals change in distance divided by time. Convert the distance from the ridge to centimeters and the time to years, then divide. For example, rock 600 km from a ridge that is 30 million years old gives 60,000,000 cm divided by 30,000,000 years, which is 2 cm per year. Check whether the question asks for one side of the ridge or the full ocean widening, which is twice as fast.

What is the order of Earth's interior layers and how do we know the outer core is liquid?

From the surface inward: crust (thin, solid), mantle (thick, solid but slowly flowing), outer core (liquid iron and nickel), inner core (solid iron and nickel). Temperature, pressure and density all increase with depth, as shown on the Inferred Properties of Earth's Interior page, and the crust-mantle boundary is the Moho. We know the outer core is liquid because S-waves, which travel only through solids, cannot pass through it and create an S-wave shadow zone on the far side of Earth.

New YorkEarth and Environmental Science

Identifying rocks and minerals with the Reference Tables: the lithosphere unit for the NY Regents

A deep-dive guide to the lithosphere unit for the NY Regents: how to use the Properties of Common Minerals chart, the Scheme for Igneous Rock Identification and the sedimentary and metamorphic charts, plus reading Earth's interior, plate boundaries and the earthquake travel-time graph, so you earn the Reference Tables marks on every rock, mineral and tectonics question.

Generated by Claude Opus 4.819 min readESCI-LITHOUpdated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

The lithosphere unit is a Reference Tables unit
Identifying a mineral, step by step
The Scheme for Igneous Rock Identification
Sedimentary and metamorphic charts
Earth's interior and plate boundaries
The earthquake travel-time graph
A worked spreading-rate calculation
Check your knowledge

The lithosphere unit is a Reference Tables unit

More than any other part of the course, the lithosphere rewards students who can read the Reference Tables charts under pressure. The rock and mineral questions are almost all chart questions: NYSED gives you the Properties of Common Minerals chart, the Scheme for Igneous Rock Identification, the sedimentary and metamorphic charts, the Inferred Properties of Earth's Interior page, the Tectonic Plates map and the earthquake travel-time graph, then writes questions that only make sense if you can use them. This guide ties the lithosphere dot-point pages together: minerals and their properties, the rock cycle and igneous rocks, sedimentary and metamorphic rocks, plate tectonics and Earth's interior and earthquakes and seismic waves.

Identifying a mineral, step by step

The chart lists, for each mineral, its luster, hardness, cleavage or fracture, color, streak, a distinguishing characteristic, a common use and the chemical composition. The reliable order is:

Luster. Metallic (pyrite, galena, magnetite) or nonmetallic (quartz, feldspar, calcite, mica).
Hardness. Use field references: a fingernail scratches up to about 2.5, a copper penny to about 3.5, a steel file or glass to about 5.5.
Breakage. Cleavage (flat, repeatable planes, like mica's sheets or halite's cubes) or fracture (uneven, like quartz).
A distinguishing test. The acid fizz for calcite, the salty taste of halite, the magnetism of magnetite.

The Scheme for Igneous Rock Identification

This is the single most-tested chart in the unit. Read it in two directions:

Down the chart (texture): coarse (large crystals) at the top means slow cooling, intrusive; fine (small crystals) below means fast cooling, extrusive; glassy at the bottom means very fast cooling.
Across the chart (composition): the left side is felsic (light color, low density, rich in quartz and feldspar); the right side is mafic (dark color, high density, rich in pyroxene and olivine).

So the chart gives a grid: coarse and felsic is granite; fine and felsic is rhyolite; coarse and mafic is gabbro; fine and mafic is basalt. The chart also shows that density and color increase from felsic to mafic, and that the percentage of each mineral changes across it.

Sedimentary and metamorphic charts

The sedimentary chart splits into clastic rocks (named by particle size: conglomerate, sandstone, siltstone, shale) and chemical/biologic rocks (named by composition: rock salt, limestone, coal). The metamorphic chart splits into foliated rocks (banded by directed pressure: slate, phyllite, schist, gneiss) and nonfoliated rocks (marble from limestone, quartzite from sandstone). The chart shows the parent rock for each metamorphic rock and the grade increasing from slate to gneiss.

Earth's interior and plate boundaries

The Inferred Properties of Earth's Interior page shows temperature, pressure and density rising with depth, the crust, mantle, outer core and inner core, and the Moho (crust-mantle boundary). The Tectonic Plates map shows the plates, their boundaries (divergent, convergent, transform), hot spots, and the locations of major earthquakes and volcanoes, which cluster along boundaries. Read these together to explain why the Ring of Fire exists or why a region has frequent earthquakes.

The earthquake travel-time graph

Distance, origin time and three stations

A station records a P-wave at 14:30:00 and an S-minus-P time of 6 minutes. Work the full epicenter problem.

step 1 Distance from the S-P time

On the travel-time graph, find where the vertical gap between the S and P curves equals 6 minutes (mark the gap on a paper edge, slide it between the curves), then read down: about 4,000 km (accept the NYSED range).

step 2 P-wave travel time

For 4,000 km, the P-wave travel time read off the graph is about 7 minutes.

step 3 Origin time

Origin time equals arrival minus travel time: $14{:}30{:}00 - 7\ \text{min} = 14{:}23{:}00$ .

step 4 Stations needed

This station gives only a circle of possible epicenters. Three stations are needed so three circles intersect at the single epicenter (triangulation).

A worked spreading-rate calculation

Sea-floor spreading rate

Matching magnetic stripes are 750 km from a mid-ocean ridge, and the rock there is 25 million years old. Find the spreading rate on that side in cm/year.

step 1 Write the equation

From page 1: $\text{rate} = \dfrac{\text{change in distance}}{\text{time}}$ .

step 2 Convert units

$750\ \text{km} = 75{,}000{,}000\ \text{cm}$ ; the time is $25{,}000{,}000$ years.

step 3 Compute

$\text{rate} = \dfrac{75{,}000{,}000\ \text{cm}}{25{,}000{,}000\ \text{years}} = 3\ \text{cm/year}$ .

step 4 Check the side

This is one side of the ridge. The full ocean widens at about 6 cm/year (both sides combined).

Check your knowledge

Attempt these with the Reference Tables open, then check against the solutions.

State the order to use the Properties of Common Minerals chart when identifying an unknown. (2 marks)
A coarse-grained, dark, dense igneous rock: name it and state where it cooled. (2 marks)
A rock made of cemented sand-sized grains: classify it and name it. (2 marks)
Name the metamorphic rocks formed from shale, in order of increasing grade. (2 marks)
State how the S-wave shadow zone shows the outer core is liquid. (2 marks)
Rock 1,000 km from a ridge is 40 million years old. Find the spreading rate. (2 marks)
State why three seismic stations are needed to locate an epicenter. (2 marks)

Solutions

Q1: Luster first, then hardness, then cleavage or fracture, then a distinguishing test (and use streak over color).
Q2: Gabbro; it cooled slowly deep below the surface (intrusive), giving large crystals, and is mafic (dark, dense).
Q3: A clastic sedimentary rock; sand-sized grains make it sandstone.
Q4: Shale to slate to phyllite to schist to gneiss.
Q5: S-waves travel only through solids, so they cannot pass through the liquid outer core, producing an S-wave shadow zone on the far side of Earth.
Q6: $1{,}000\ \text{km} = 100{,}000{,}000\ \text{cm}$ ; $\dfrac{100{,}000{,}000}{40{,}000{,}000} = 2.5\ \text{cm/year}$ .
Q7: Each station's distance gives a circle of possible epicenters; two circles cross at two points, so three circles are needed to intersect at one point.

Sources & how we know this

Reference Tables for Physical Setting/Earth Science (2011 edition) — New York State Education Department (2011)
Regents Examination in Physical Setting/Earth Science — New York State Education Department (2026)